Modify input limits for apply_scale_32

Aligns with change in specification, as the limit to value being between
(-1 << shift-2) and (1 << shift-2) was overly constraining.

Signed-off-by: Eric Kunze <eric.kunze@arm.com>
Change-Id: I72cc5743344d4036920c3df366e0a3930701a0cb