ASoC: fix rockchip 64-bit build warning

The rk_spdif_probe uses the device match data as a token to identify a
particular device, but accidentally casts a pointer to 'int', which is
not portable, as gcc points out in this warning on arm64:

rockchip_spdif.c: In function 'rk_spdif_probe':
rockchip_spdif.c:283:6: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]

This changes the logic to compare two pointer values instead, using
the same cast that was used for initializing the value in the first
place.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Mark Brown <broonie@kernel.org>