arm64: Use defines instead of magic numbers

Following assembly code is not trivial; make it slightly easier to read by
replacing some of the magic numbers with the defines which are already
present in sysreg.h.
Reviewed-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm64/include/asm/assembler.h

@@ -442,8 +442,8 @@ USER(\label, ic	ivau, \tmp2)			// invalidate I line PoU
  * reset_pmuserenr_el0 - reset PMUSERENR_EL0 if PMUv3 present
  */
 	.macro	reset_pmuserenr_el0, tmpreg
-	mrs	\tmpreg, id_aa64dfr0_el1	// Check ID_AA64DFR0_EL1 PMUVer
-	sbfx	\tmpreg, \tmpreg, #8, #4
+	mrs	\tmpreg, id_aa64dfr0_el1
+	sbfx	\tmpreg, \tmpreg, #ID_AA64DFR0_PMUVER_SHIFT, #4
 	cmp	\tmpreg, #1			// Skip if no PMU present
 	b.lt	9000f
 	msr	pmuserenr_el0, xzr		// Disable PMU access from EL0

arch/arm64/kernel/head.S

@@ -505,7 +505,7 @@ ENTRY(el2_setup)
 	 * kernel is intended to run at EL2.
 	 */
 	mrs	x2, id_aa64mmfr1_el1
-	ubfx	x2, x2, #8, #4
+	ubfx	x2, x2, #ID_AA64MMFR1_VHE_SHIFT, #4
 #else
 	mov	x2, xzr
 #endif
@@ -538,7 +538,7 @@ set_hcr:
 #ifdef CONFIG_ARM_GIC_V3
 	/* GICv3 system register access */
 	mrs	x0, id_aa64pfr0_el1
-	ubfx	x0, x0, #24, #4
+	ubfx	x0, x0, #ID_AA64PFR0_GIC_SHIFT, #4
 	cbz	x0, 3f
 
 	mrs_s	x0, SYS_ICC_SRE_EL2
@@ -564,8 +564,8 @@ set_hcr:
 #endif
 
 	/* EL2 debug */
-	mrs	x1, id_aa64dfr0_el1		// Check ID_AA64DFR0_EL1 PMUVer
-	sbfx	x0, x1, #8, #4
+	mrs	x1, id_aa64dfr0_el1
+	sbfx	x0, x1, #ID_AA64DFR0_PMUVER_SHIFT, #4
 	cmp	x0, #1
 	b.lt	4f				// Skip if no PMU present
 	mrs	x0, pmcr_el0			// Disable debug access traps
@@ -574,7 +574,7 @@ set_hcr:
 	csel	x3, xzr, x0, lt			// all PMU counters from EL1
 
 	/* Statistical profiling */
-	ubfx	x0, x1, #32, #4			// Check ID_AA64DFR0_EL1 PMSVer
+	ubfx	x0, x1, #ID_AA64DFR0_PMSVER_SHIFT, #4
 	cbz	x0, 7f				// Skip if SPE not present
 	cbnz	x2, 6f				// VHE?
 	mrs_s	x4, SYS_PMBIDR_EL1		// If SPE available at EL2,