openrisc: linker: Use zephyr's convention for rodata

Zephyr maps the start and end of the rodata section with variables using
the __rodata_region_start and __rodata_region_end. This patch adopts this
convention for the OpenRISC architecture.

Signed-off-by: Joel Holdsworth <jholdsworth@nvidia.com>

Author: jhol

include/zephyr/linker/utils.h

@@ -36,7 +36,8 @@ static inline bool linker_is_in_rodata(const void *addr)
 #if defined(CONFIG_ARM) || defined(CONFIG_ARC) || defined(CONFIG_X86) || \
 	defined(CONFIG_ARM64) || defined(CONFIG_NIOS2) || \
 	defined(CONFIG_RISCV) || defined(CONFIG_SPARC) || \
-	defined(CONFIG_MIPS) || defined(CONFIG_XTENSA)
+	defined(CONFIG_MIPS) || defined(CONFIG_XTENSA) || \
+	defined(CONFIG_OPENRISC)
 	extern char __rodata_region_start[];
 	extern char __rodata_region_end[];
 	#define RO_START __rodata_region_start