USB: gadget: qdss: Fix strncmp length usage

Using a newer GCC we get the following warnings:

drivers/usb/gadget/f_qdss.c: In function 'qdss_bind_config':
drivers/usb/gadget/f_qdss.c:598: warning: argument to 'sizeof' in
'strncmp' call is the same expression as the second source; did you mean
to provide an explicit length? [-Wsizeof-pointer-memaccess]

drivers/usb/gadget/f_qdss.c: In function 'usb_qdss_open':
drivers/usb/gadget/f_qdss.c:760: warning: argument to 'sizeof' in
'strncmp' call is the same expression as the second source; did you mean
to provide an explicit length? [-Wsizeof-pointer-memaccess]

These look to be due to using sizeof(ch->name) which is a pointer, use
a simple strcmp instead.

Change-Id: I09e09a18ffb3361fc351b177ed3a35432d9ed933
Signed-off-by: Kumar Gala <galak@codeaurora.org>