depend-cleanup.sh: Simplify handling for stale syscall.S

Remove the outer grep and depend on the greps in clean_dep instead.

tools/build/depend-cleanup.sh

@@ -235,9 +235,7 @@ clean_dep   lib/libc        statfs        c
 # 20240308  e6ffc7669a56    Remove pointless MD syscall(2)
 # 20240308  0ee0ae237324    Remove pointless MD syscall(2)
 # 20240308  7b3836c28188    Remove pointless MD syscall(2)
-if [ ${MACHINE} != i386 -a -f "$OBJTOP"/lib/libsys/.depend.syscall.o ] && \
-    grep -q -e 'libsys/[^ /]*/syscall.S' "$OBJTOP"/lib/libsys/.depend.syscall.*; then
-	echo "Removing stale <arch>/syscall.S depends"
+if [ ${MACHINE} != i386 ]; then
 	clean_dep   lib/libsys  syscall S
 	clean_dep   lib/libc    syscall S
 fi