staging: dwc2: simplify register shift expressions

This commit changes expressions from (val >> shift) & (mask >> shift) to
(val & mask) >> shift.

Signed-off-by: Matthijs Kooijman <matthijs@stdin.nl>
Acked-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>