arm64/sysreg: Remove unused define ARM64_FEATURE_FIELD_BITS

The define ARM64_FEATURE_FIELD_BITS is now unused and feature id
fields don't always have 4 bits. Remove it.

Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Author: benhor01

arch/arm64/include/asm/sysreg.h

@@ -1129,8 +1129,6 @@
 #define gicr_insn(insn)			read_sysreg_s(GICV5_OP_GICR_##insn)
 #define gic_insn(v, insn)		write_sysreg_s(v, GICV5_OP_GIC_##insn)
 
-#define ARM64_FEATURE_FIELD_BITS	4
-
 #ifdef __ASSEMBLY__
 
 	.macro	mrs_s, rt, sreg