lib/os: cbprintf_packaged: simplify rodata check

NIOS2 is using _image_rodata_start/_end in its linker script
to mark the boundaries of rodata. So they no loner need
special treatment.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>
diff --git a/lib/os/cbprintf_packaged.c b/lib/os/cbprintf_packaged.c
index 57daa50..96b519b 100644
--- a/lib/os/cbprintf_packaged.c
+++ b/lib/os/cbprintf_packaged.c
@@ -30,16 +30,12 @@
 #define RO_START 0
 #define RO_END 0
 #elif defined(CONFIG_ARC) || defined(CONFIG_ARM) || defined(CONFIG_X86) \
-	|| defined(CONFIG_RISCV) || defined(CONFIG_ARM64)
+	|| defined(CONFIG_RISCV) || defined(CONFIG_ARM64) \
+	|| defined(CONFIG_NIOS2)
 	extern char _image_rodata_start[];
 	extern char _image_rodata_end[];
 #define RO_START _image_rodata_start
 #define RO_END _image_rodata_end
-#elif defined(CONFIG_NIOS2) || defined(CONFIG_RISCV)
-	extern char _image_rom_start[];
-	extern char _image_rom_end[];
-#define RO_START _image_rom_start
-#define RO_END _image_rom_end
 #elif defined(CONFIG_XTENSA)
 	extern char _rodata_start[];
 	extern char _rodata_end[];