ASoC: cx2072x: fix integer overflow on unsigned int multiply

In the case where frac_div larger than 96 the result of an unsigned
multiplication overflows an unsigned int.  For example, this can
happen when the sample_rate is 192000 and pll_input is 122.  Fix
this by casing the first term of the mutiply to a u64. Also remove
the extraneous parentheses around the expression.

Addresses-Coverity: ("Unintentional integer overflow")
Fixes: a497a436 ("ASoC: Add support for Conexant CX2072X CODEC")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Mark Brown <broonie@kernel.org>