ARM: 8126/1: crypto: enable NEON SHA-384/SHA-512 for big endian

The SHA-512 NEON works just fine under big endian, so remove the Kconfig
condition preventing it from being selected if CONFIG_CPU_BIG_ENDIAN is
set.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>