usb: gadget: uvc: Fix ERR_PTR dereference in uvc_v4l2.c

usb: gadget: uvc: Fix ERR_PTR dereference in uvc_v4l2.c

Fix potential dereferencing of ERR_PTR() in find_format_by_pix()
and uvc_v4l2_enum_format().

Fix the following smatch errors:

drivers/usb/gadget/function/uvc_v4l2.c:124 find_format_by_pix()
error: 'fmtdesc' dereferencing possible ERR_PTR()

drivers/usb/gadget/function/uvc_v4l2.c:392 uvc_v4l2_enum_format()
error: 'fmtdesc' dereferencing possible ERR_PTR()

Also, fix similar issue in uvc_v4l2_try_format() for potential
dereferencing of ERR_PTR().

Signed-off-by: Abhishek Tamboli <abhishektamboli9@gmail.com>
Link: https://lore.kernel.org/r/20240815102202.594812-1-abhishektamboli9@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>