arm64: arch_timer: Add workaround for ARM erratum 1188873

When running on Cortex-A76, a timer access from an AArch32 EL0
task may end up with a corrupted value or register. The workaround for
this is to trap these accesses at EL1/EL2 and execute them there.

This only affects versions r0p0, r1p0 and r2p0 of the CPU.

Change-Id: If2026eff975725d41dc2f1630ab086f3cc7deea3
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Git-commit: 95b861a4a6d94f64d5242605569218160ebacdbe
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


[neeraju@codeaurora: Resolve trivial merge conflicts.]
Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>