ASoC: ad1980: Replace goto loop with do-while loop

Using a proper do-while loop here instead of a open-coded goto loop is both
cleaner and shorter.

Also fixes the following warnings from smatch:
	sound/soc/codecs/ad1980.c:213 ad1980_reset() info: loop could be replaced with if statement.
	sound/soc/codecs/ad1980.c:212 ad1980_reset() info: ignoring unreachable code.
	sound/soc/codecs/ad1980.c:215 ad1980_reset() info: ignoring unreachable code.

While we are at it also change retry_cnt to unsigned int, using u16 for a
on-stack loop counter doesn't make that much sense.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@linaro.org>