usb: gadget: pxa27x: Remove redundant assignment to is_short and dev

Variable is_short is set to zero but this value is never read as it is
overwritten with a new value later on, hence it is a redundant
assignment and can be removed.  Pointer dev is assigned a value that
is not read and it is updated a few statements later, this too is
redundant and can be removed. Cleans up clan warnings:

drivers/usb/gadget/udc/pxa27x_udc.c:986:3: warning: Value stored
to 'is_short' is never read
drivers/usb/gadget/udc/pxa27x_udc.c:1141:2: warning: Value stored
to 'dev' is never read

Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>