arm: traps: emulate a MRCC instruction reading CNTPCT register

A user space application is planned to support feature for
synchronized timestamp among debug packets across peripherals.
As part of the feature, it is responsible for providing physical
timer count value to user space. If memory mapped timer is used
in ARM arch, Usersapce can't read the physical timer count directly
with a MRCC ASM instruction. So Kernel traps the instruction and
returns the physical timer count.

Change-Id: Ia3f0d9c8c06ca9e2204187890c0c57c8640e4f7e
Signed-off-by: Se Wang (Patrick) Oh <sewango@codeaurora.org>