This reverts the non-ARM portions of 97999919bb.
x86_64 perlasm already makes .globl imply .hidden. (Confusingly, ARM does not.)
Since we don't need it, revert those to minimize divergence with upstream.

Change-Id: I2d205cfb1183e65d4f18a62bde187d206b1a96de
Reviewed-on: https://boringssl-review.googlesource.com/3610
Reviewed-by: Adam Langley <agl@google.com>