xhci: Remove BUG_ON() in xhci_alloc_container_ctx.

It's horrible coding style to panic the kernel when someone passes you
an argument value you didn't expect.  In the future, we may want to add
additional context types, so it's better to gracefully handle additional
context types instead of panicking.
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: John Youn <johnyoun@synopsys.com>

drivers/usb/host/xhci-mem.c

@@ -358,11 +358,15 @@ int xhci_ring_expansion(struct xhci_hcd *xhci, struct xhci_ring *ring,
 static struct xhci_container_ctx *xhci_alloc_container_ctx(struct xhci_hcd *xhci,
 						    int type, gfp_t flags)
 {
-	struct xhci_container_ctx *ctx = kzalloc(sizeof(*ctx), flags);
+	struct xhci_container_ctx *ctx;
+
+	if ((type != XHCI_CTX_TYPE_DEVICE) && (type != XHCI_CTX_TYPE_INPUT))
+		return NULL;
+
+	ctx = kzalloc(sizeof(*ctx), flags);
 	if (!ctx)
 		return NULL;
 
-	BUG_ON((type != XHCI_CTX_TYPE_DEVICE) && (type != XHCI_CTX_TYPE_INPUT));
 	ctx->type = type;
 	ctx->size = HCC_64BYTE_CONTEXT(xhci->hcc_params) ? 2048 : 1024;
 	if (type == XHCI_CTX_TYPE_INPUT)