mmc: fsl: Use brackets around if()

At present the IS_ENABLED() macro has extra brackets, making it possible
to write:

   if IS_ENABLED(CONFIG_XXX)

but it is a bit confusing. Add the missing brackets.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
diff --git a/drivers/mmc/fsl_esdhc_imx.c b/drivers/mmc/fsl_esdhc_imx.c
index 9299635..08ea98f 100644
--- a/drivers/mmc/fsl_esdhc_imx.c
+++ b/drivers/mmc/fsl_esdhc_imx.c
@@ -453,7 +453,7 @@
 
 	/* Send the command */
 	esdhc_write32(&regs->cmdarg, cmd->cmdarg);
-	if IS_ENABLED(CONFIG_FSL_USDHC) {
+	if (IS_ENABLED(CONFIG_FSL_USDHC)) {
 		u32 mixctrl = esdhc_read32(&regs->mixctrl);
 
 		esdhc_write32(&regs->mixctrl,