Enable arm64 neon scrypt implementation

It seems that old Scrypt-config.mk is unaware of arm64 architecture.
In fact, crypto_scrypt-neon.c can be compiled into arm64 as well.  This
CL adds an arch section for arm64.

Bug: 65425184
Test: adb shell /data/nativetest64/scrypt_test/scrypt_test
Change-Id: Ib451de642c7cc4548bfdc0879781981654b21b8f
Merged-In: If40a30378b8038324aad44071107130d7722e28d
2 files changed