arm: Change access permission in TPIDRURO and TPIDRURW

arm: Change access permission in TPIDRURO and TPIDRURW

This patch corrects the TPIDRURO and TPIDRURW access flags: TPIDRURO is
now readable in secure user mode, an TPIDRURW is readable and writable
in secure user mode.

Change-Id: I6293d9a3bcc7adc0f655bf98d29aca51eca5a002
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Chuan Zhu <chuan.zhu@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/6381
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>