ASoC: tlv320aic31xx: Check clock and divider before division

If our set_sysclk DAI callback has not been called yet p_div will be 0
and dividing by this will cause an error. Print an error message and
leave before this.

Signed-off-by: Andrew F. Davis <afd@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>