udc: lpc32xx: fix 64-bit compiler warning

gcc points out a suspicious cast from a pointer to an 'int' when
compile-testing on 64-bit architectures.

drivers/usb/gadget/udc/lpc32xx_udc.c: In function ‘udc_pop_fifo’:
drivers/usb/gadget/udc/lpc32xx_udc.c:1156:11: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
drivers/usb/gadget/udc/lpc32xx_udc.c: In function ‘udc_stuff_fifo’:
drivers/usb/gadget/udc/lpc32xx_udc.c:1257:11: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]

The code works find, but it's easy enough to change the cast to
a uintptr_t to shut up that warning.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20190918200201.2292008-1-arnd@arndb.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>