kbuild: Add '-fms-extensions' to areas with dedicated CFLAGS

kbuild: Add '-fms-extensions' to areas with dedicated CFLAGS

This is a follow up to commit c4781dc3d1cf ("Kbuild: enable
-fms-extensions") but in a separate change due to being substantially
different from the initial submission.

There are many places within the kernel that use their own CFLAGS
instead of the main KBUILD_CFLAGS, meaning code written with the main
kernel's use of '-fms-extensions' in mind that may be tangentially
included in these areas will result in "error: declaration does not
declare anything" messages from the compiler.

Add '-fms-extensions' to all these areas to ensure consistency, along
with -Wno-microsoft-anon-tag to silence clang's warning about use of the
extension that the kernel cares about using. parisc does not build with
clang so it does not need this warning flag. LoongArch does not need it
either because -W flags from KBUILD_FLAGS are pulled into cflags-vdso.

Reported-by: Christian Brauner <brauner@kernel.org>
Closes: https://lore.kernel.org/20251030-meerjungfrau-getrocknet-7b46eacc215d@brauner/
Reviewed-by: Christian Brauner <brauner@kernel.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>