Fix Unisoc T618 Chipset Detection

[bc-lee]

Add support for uppercase "UNISOC T" prefix in match_t function to handle devices like Samsung Galaxy Tab A8 (SM-X205N) that report "UNISOC T618" instead of the expected mixed-case "Unisoc T618".

The function now explicitly matches both variants:

• "Unisoc T" (mixed case, existing)
• "UNISOC T" (uppercase, new)

This ensures proper chipset vendor detection on affected Samsung devices where the uppercase variant caused match failures.

Includes test case for "UNISOC T618" detection.
Fixes #306

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[fbarchard]

Change looks okay and consistent with documentation I find on Galaxy Tab A8

With this change does T618 fill in chipset->model correctly?
Does the T618 require any ISA override? Example vudot is problematic on T310
https://github.com/pytorch/cpuinfo/blob/main/src/arm/linux/aarch32-isa.c#L148-L151

[bc-lee]

I checked out XNNPACK and built and ran all tests on my T618 device. Fortunately, I didn’t encounter any SIGILL issues.

The only failures were a few numerical differences in the f32-vgelu-test, and only in the scalar mode—not in the NEON paths. I don't think this is significant, and I believe we don't need to worry about scalar-only cases in cpuinfo.

For reference, here’s an example output from one of the failing scalar-mode tests:

[ RUN      ] xnn_f32_vgelu_ukernel__scalar_rational_12_10_div_u8.inplace
/path/to/XNNPACK/./test/vunary-microkernel-tester.h:187: Failure
The difference between x[i] and y_ref[i] is 1.4374899101991961e-06, which exceeds test_info.Tolerance(y_ref[i], xnn_datatype_of<Out>()), where
x[i] evaluates to -1.437489913769241e-06,
y_ref[i] evaluates to -3.5700448199342712e-15, and
test_info.Tolerance(y_ref[i], xnn_datatype_of<Out>()) evaluates to 1.1920928955078125e-06.
at 0 / 1, x[0] = -8.03902626037597656e+00
Google Test trace:
/path/to/XNNPACK/./test/replicable_random_device.h:79: To replicate this failure, re-run the test with `--gunit_random_seed=54411`.

/path/to/XNNPACK/./test/vunary-microkernel-tester.h:187: Failure
The difference between x[i] and y_ref[i] is 1.4374899101991961e-06, which exceeds test_info.Tolerance(y_ref[i], xnn_datatype_of<Out>()), where
x[i] evaluates to -1.437489913769241e-06,
y_ref[i] evaluates to -3.5700448199342712e-15, and
test_info.Tolerance(y_ref[i], xnn_datatype_of<Out>()) evaluates to 1.1920928955078125e-06.
at 1 / 8, x[1] = -8.03902626037597656e+00
Google Test trace:
/path/to/XNNPACK/./test/replicable_random_device.h:79: To replicate this failure, re-run the test with `--gunit_random_seed=54411`.

[  FAILED  ] xnn_f32_vgelu_ukernel__scalar_rational_12_10_div_u8.inplace (0 ms)

If you have other good ways to validate the instruction set on this device, please let me know.