autoconf: fix arch.h selection for arm*

[claudioandre-br]

As it is now, it ends up picking arm32le.h on Android.

Configured for building John the Ripper jumbo:
Target CPU ......................................... arm, 64-bit LE
Target OS .......................................... linux-gnueabi
Cross compiling .................................... no
Legacy arch header ................................. arm32le.h

Tested (because of #5631, I have to force SIMD disabled):

Target CPU ......................................... arm (SIMD disabled), 64-bit LE
Target OS .......................................... linux-gnueabi
Cross compiling .................................... no
Legacy arch header ................................. arm64le.h

[magnumripper]

This looks right. I fixed this same problem in d6c8792 but apparently only for SIMD.

[magnumripper]

Tested this on Macbook, problem triggered when using --disable-simd, and it was fixed with this commit