ARM: hw_breakpoint: use CRn as argument for debug reg accessor macros

ARM: hw_breakpoint: use CRn as argument for debug reg accessor macros

The coprocessor register CRn for accesses to the debug register can be a
different one than C0. Take this into account for the ARM_DBG_READ and
the ARM_DBG_WRITE macro.

The inline assembler calls which used a coprocessor register CRn other
than C0 are replaced by the ARM_DBG_READ or ARM_DBG_WRITE macro.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>