phy: ralink: fix 64-bit build warning

Casting between an 'int' and a pointer causes a warning on
64-bit architectures in compile-testing this driver:

drivers/phy/ralink/phy-ralink-usb.c: In function 'ralink_usb_phy_probe':
drivers/phy/ralink/phy-ralink-usb.c:195:13: error: cast from pointer to
integer of different size [-Werror=pointer-to-int-cast]

This changes the code to cast to uintptr_t instead. This is
guaranteed to do what we want on all architectures and avoids
the warning.

Fixes: 2411a736 ("phy: ralink-usb: add driver for Mediatek/Ralink")
Acked-by: John Crispin <john@phrozen.org>
Tested-by Harvey Hunt <harvey.hunt@imgtec.com>
Reviewed-by Harvey Hunt <harvey.hunt@imgtec.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>