arch-arm: IMPDEF for SYS instruction with CRn = {11, 15}

arch-arm: IMPDEF for SYS instruction with CRn = {11, 15}

According to the arm arm, a SYS instruction (op0 = 1) with CRn = (11 or
15) is implementation defined; this makes it trappable by having
HCR_EL2.TIDCP = 1.

Change-Id: Idd94ac345fee652ee6f8c0a7eb7b06ac75ec38ef
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/13780
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>