usb: gadget: ci: Avoid null pointer dereference

The ci_req->hw_buf can be NULL, test whether it is and if so,
avoid accessing it. Else, the system may crash.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Peter Chen <peter.chen@nxp.com>
Cc: Li Jun <jun.li@nxp.com>
Cc: Peng Fan <peng.fan@nxp.com>
diff --git a/drivers/usb/gadget/ci_udc.c b/drivers/usb/gadget/ci_udc.c
index 226a9e6..542684c 100644
--- a/drivers/usb/gadget/ci_udc.c
+++ b/drivers/usb/gadget/ci_udc.c
@@ -402,6 +402,9 @@
 
 flush:
 	hwaddr = (unsigned long)ci_req->hw_buf;
+	if (!hwaddr)
+		return 0;
+
 	aligned_used_len = roundup(req->length, ARCH_DMA_MINALIGN);
 	flush_dcache_range(hwaddr, hwaddr + aligned_used_len);
 
@@ -415,7 +418,7 @@
 	unsigned long hwaddr = (unsigned long)ci_req->hw_buf;
 	uint32_t aligned_used_len;
 
-	if (in)
+	if (in || !hwaddr)
 		return;
 
 	aligned_used_len = roundup(req->actual, ARCH_DMA_MINALIGN);