adsp: boot: power: Fixed used register name

The code used the name DFDSPBRCP referring to the DSP Boot / Recovery
Capability Pointer register from DSP Subsystem Capability / Status
Registers range. The address used, however, pointed to DSP Core Shim
(DSPCS) registers block. Changed define names to not be misleading.

Signed-off-by: Adrian Warecki <adrian.warecki@intel.com>