ARM: add .gitignore entry for aesbs-core.S

This avoids this file being incorrectly added to git.

Change-Id: I593c571982ebf944efa43429b5f0d25d0f281c4a
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Git-commit: 9d691d9e8e573ec4205cca8d20777c8f27c7dc69
Git-repo: https://android.googlesource.com/kernel/common/


Signed-off-by: Samir Mehta <samirn@codeaurora.org>