The change removes some unnecessary and incorrect code for EXTR_S.H.
Further, it corrects the mask for shift value in the EXTR_ instructions. It also
extends the existing tests so they trigger the issues corrected with the change.
Signed-off-by: Petar Jovanovic <petarj@mips.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>