phy: usb: Fix misuse of IS_ENABLED

While IS_ENABLED() is perfectly fine for CONFIG_* symbols, it is not
for other symbols such as __BIG_ENDIAN that is provided directly by
the compiler.

Switch to use CONFIG_CPU_BIG_ENDIAN instead of __BIG_ENDIAN.

Signed-off-by: Chen Li <[e-mail]>
Reviewed-by: Al Cooper <[e-mail]>
Acked-by: Florian Fainelli <[e-mail]>
Fixes: 94583a41047e ("phy: usb: Restructure in preparation for adding 7216 USB support")
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

drivers/phy/broadcom/phy-brcm-usb-init.h

···
 	 * Other architectures (e.g., ARM) either do not support big endian, or
 	 * else leave I/O in little endian mode.
 	 */
-	if (IS_ENABLED(CONFIG_MIPS) && IS_ENABLED(__BIG_ENDIAN))
+	if (IS_ENABLED(CONFIG_MIPS) && IS_ENABLED(CONFIG_CPU_BIG_ENDIAN))
 		return __raw_readl(addr);
 	else
 		return readl_relaxed(addr);
···
 static inline void brcm_usb_writel(u32 val, void __iomem *addr)
 {
 	/* See brcmnand_readl() comments */
-	if (IS_ENABLED(CONFIG_MIPS) && IS_ENABLED(__BIG_ENDIAN))
+	if (IS_ENABLED(CONFIG_MIPS) && IS_ENABLED(CONFIG_CPU_BIG_ENDIAN))
 		__raw_writel(val, addr);
 	else
 		writel_relaxed(val, addr);