ASoC: change mask in snd_soc_get/put_volsw_sx to unsigned int

If the result of (min + max) is negative in functions
snd_soc_get_volsw_sx() or snd_soc_put_volsw_sx(), there
will be an overflow for the variable 'mask'.
   UBSAN: Undefined behaviour in sound/soc/soc-ops.c:382:6
   signed integer overflow:
   -2147483648 - 1 cannot be represented in type 'int'

Fix this by updating the variable type of 'mask' to unsigned int.

Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>
Signed-off-by: Mark Brown <broonie@kernel.org>