tools: arm64: Import sysreg.h

Bring-in the kernel's arch/arm64/include/asm/sysreg.h
into tools/ for arm64 to make use of all the standard
register definitions in consistence with the kernel.

Make use of the register read/write definitions from
sysreg.h, instead of the existing definitions. A syntax
correction is needed for the files that use write_sysreg()
to make it compliant with the new (kernel's) syntax.

Reviewed-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Oliver Upton <oupton@google.com>
Signed-off-by: Raghavendra Rao Ananta <rananta@google.com>
[maz: squashed two commits in order to keep the series bisectable]
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211007233439.1826892-3-rananta@google.com
Link: https://lore.kernel.org/r/20211007233439.1826892-4-rananta@google.com