feat(aarch64): add DBGPRCR_EL1 register accessors

This is a small change adding accessor functions for the Debug Power
Control register (DBGPRCR_EL1) to the common architectural helpers.

Change-Id: I72261fbf0395d900347b46af320093ed946aa73d
Signed-off-by: Chris Kay <chris.kay@arm.com>
diff --git a/include/arch/aarch64/arch_helpers.h b/include/arch/aarch64/arch_helpers.h
index 3f3f14d..8b92f19 100644
--- a/include/arch/aarch64/arch_helpers.h
+++ b/include/arch/aarch64/arch_helpers.h
@@ -295,6 +295,7 @@
 DEFINE_SYSREG_RW_FUNCS(dbgdtrtx_el0)
 DEFINE_SYSREG_RW_FUNCS(sp_el1)
 DEFINE_SYSREG_RW_FUNCS(sp_el2)
+DEFINE_SYSREG_RW_FUNCS(dbgprcr_el1)
 
 DEFINE_SYSOP_FUNC(wfi)
 DEFINE_SYSOP_FUNC(wfe)