usb: gadget: goku_udc: Fix mask and set operation on variable master

usb: gadget: goku_udc: Fix mask and set operation on variable master

The variable master is being masked with ~MST_R_BITS however this
masked value is never used, the following updates to master are
assignments. I suspect the original intention was to mask out the
MST_R_BITS and then bit-wise or in the appropriate read bits rather
than perform an assignment. Fix this by using the |= operator rather
than a straight assignment.

Note that this code is pre-git history, so I can't find a sha for
it.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Addresses-Coverity: ("Unused value")
Link: https://lore.kernel.org/r/20210910163131.94796-1-colin.king@canonical.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>