usb_dev: Do not erroneously return QIPROG_SUCCESS (Trivial)

Do not return QIRPOG_SUCCES in the control request handler if
qiprog_get_capabilities returns an error.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
usb_dev: wValue is 16-bits, not 8 bits (Trivial)

wValue was declared as a 8-bit value in qiprog_handle_control_request, but
it is 16-bits. Fix this error.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>