asm-generic: Remove redundant arch-specific rules for simd.h

Now that simd.h is in include/asm-generic/Kbuild we don't need
the arch-specific Kbuild rules for them.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Fixes: 82cb5485 ("asm-generic: make simd.h a mandatory...")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>