crypto: arm/ghash-ce - define fpu before fpu registers are referenced

Building ARMv7 with Clang's integrated assembler leads to errors such
as:
arch/arm/crypto/ghash-ce-core.S:34:11: error: register name expected
 t3l .req d16
          ^

Since no FPU has selected yet Clang considers d16 not a valid register.
Moving the FPU directive on-top allows Clang to parse the registers and
allows to successfully build this file with Clang's integrated assembler.

Signed-off-by: Stefan Agner <stefan@agner.ch>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>