xhci: Remove BUG_ON in xhci_get_input_control_ctx.

Fail gracefully, instead of causing the kernel to panic, if the input
control context doesn't have the right type (XHCI_CTX_TYPE_INPUT).  Push
finding the pointer to the input control context up into functions that
can fail.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: John Youn <johnyoun@synopsys.com>
diff --git a/drivers/usb/host/xhci-dbg.c b/drivers/usb/host/xhci-dbg.c
index f2e7689..5d5e58f 100644
--- a/drivers/usb/host/xhci-dbg.c
+++ b/drivers/usb/host/xhci-dbg.c
@@ -553,6 +553,11 @@
 	if (ctx->type == XHCI_CTX_TYPE_INPUT) {
 		struct xhci_input_control_ctx *ctrl_ctx =
 			xhci_get_input_control_ctx(xhci, ctx);
+		if (!ctrl_ctx) {
+			xhci_warn(xhci, "Could not get input context, bad type.\n");
+			return;
+		}
+
 		xhci_dbg(xhci, "@%p (virt) @%08llx (dma) %#08x - drop flags\n",
 			 &ctrl_ctx->drop_flags, (unsigned long long)dma,
 			 ctrl_ctx->drop_flags);