ASoC: rt5663: add in missing loop counter to avoid infinite loop

The loop counter 'count' is missing an increment, so we could end up
with an infinite loop.  Add in a pre-increment to count to fix this.

Detected by CoverityScan, CID#1450120 ("Logically Dead Code")

Fixes: 1a425dbf1a10 ("ASoC: rt5663: Update the calibration funciton")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Mark Brown <broonie@kernel.org>