ArmVirtPkg: include BaseStackCheckLib also for AARCH64

ArmVirtPkg: include BaseStackCheckLib also for AARCH64

Some AArch64 toolchains also invoke the software stack checker
functions on certain code - so include BaseStackCheckLib for
AARCH64 as well as for ARM. Since this was the only difference
between [LibraryClasses.ARM] and [LibraryClasses.AARCH64],
merge the two into the existing [LibraryClasses.common].

At the same time, fix the grammar for the related comments.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18617 6f19259b-4bc3-4df7-8a09-765794883524