core: arm64: add add_imm and sub_imm assembly macros

Adds the add_imm and sub_imm assembly macros capable of adding or
subtracting a 24-bit immediate value to or from a general purpose
register.

Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Etienne Carriere <etienne.carriere@foss.st.com>

core/arch/arm/include/arm64_macros.S

@@ -116,6 +116,24 @@
 		movk    \_reg, :abs_g0_nc:\_val
 	.endm
 
+	.macro add_imm _reg, _val
+	.if ((\_val) > 0xfff)
+		add	\_reg, \_reg, ((\_val) >> 12), LSL #12
+	.endif
+	.if (((\_val) & 0xfff) > 0)
+		add	\_reg, \_reg, ((\_val) & 0xfff)
+	.endif
+	.endm
+
+	.macro sub_imm _reg, _val
+	.if ((\_val) > 0xfff)
+		sub	\_reg, \_reg, ((\_val) >> 12), LSL #12
+	.endif
+	.if (((\_val) & 0xfff) > 0)
+		sub	\_reg, \_reg, ((\_val) & 0xfff)
+	.endif
+	.endm
+
 	/*
 	 * Load address of <sym> into <reg>, <sym> being in the range
 	 * +/- 4GB of the PC (note that 'adr reg, sym' is limited to +/- 1MB).