it8xxx2: allow placing arithmetic functions in ILM

These functions are small and may be very hot depending on the workload,
so are usually a good choice to execute from RAM.

Signed-off-by: Peter Marheine <pmarheine@chromium.org>

soc/riscv/riscv-ite/it8xxx2/__arithmetic.S

@@ -10,8 +10,14 @@
  * The workaround requires the nop instruction, please don't optimize it.
  */
 
+#ifdef CONFIG_SOC_IT8XXX2_USE_ILM
+#define SECTION .__ram_code.arithmetic.
+#else
+#define SECTION .text.it8xxx2.arithmetic.
+#endif
+
 .macro __int_arithmetic func opcode
-.section .text
+.section SECTION\func
 .align 2
 .globl \func
 .type \func, @function

soc/riscv/riscv-ite/it8xxx2/linker.ld

@@ -147,6 +147,7 @@ SECTIONS
 		__ilm_flash_start = .;
 		/* Specially-tagged functions in SoC sources */
 		KEEP(*(.__ram_code))
+		*(.__ram_code.*)
 		__ilm_flash_end = .;
 		/* ILM mapping is always a multiple of 4k size; ensure following
 		 * sections won't incorrectly redirect to RAM. */