mtd: rawnand: orion: Handle cases where __LINUX_ARM_ARCH__ is not defined

Make sure __LINUX_ARM_ARCH__ is defined before testing its value.
This is needed if we want to allow selection of this driver when
COMPILE_TEST=y.
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

drivers/mtd/nand/raw/orion_nand.c

@@ -52,7 +52,7 @@ static void orion_nand_read_buf(struct mtd_info *mtd, uint8_t *buf, int len)
 {
 	struct nand_chip *chip = mtd_to_nand(mtd);
 	void __iomem *io_base = chip->IO_ADDR_R;
-#if __LINUX_ARM_ARCH__ >= 5
+#if defined(__LINUX_ARM_ARCH__) && __LINUX_ARM_ARCH__ >= 5
 	uint64_t *buf64;
 #endif
 	int i = 0;
@@ -61,7 +61,7 @@ static void orion_nand_read_buf(struct mtd_info *mtd, uint8_t *buf, int len)
 		*buf++ = readb(io_base);
 		len--;
 	}
-#if __LINUX_ARM_ARCH__ >= 5
+#if defined(__LINUX_ARM_ARCH__) && __LINUX_ARM_ARCH__ >= 5
 	buf64 = (uint64_t *)buf;
 	while (i < len/8) {
 		/*