Add missing includes

[thilinarmtb]

Description

Currently, when we run OCCA tests, they use the automatically generated *_codegen
files from the build directory. This is because, we do the following two things:

• -I${OCCA_INSTALL_DIR} is added to the compile command in device::buildKernel()
  methods.
• If OCCA_INSTALL_DIR is not defined, it defaults to OCCA_BUILD_DIR.

Since we never set OCCA_INSTALL_DIR, we have always been using *_codegen files from
the build directory. When I tried running the tests by setting OCCA_INSTALL_DIR, I get
compilation errors since we don't have the required *_codegen files at the correct places
in the install directory. This PR fixes this issue.

PS: I only tested the CMake build for now. May need fixes for the GNU Make build.

Todo

• Run the GitHub CI tests with OCCA_INSTALL_DIR set.