ASoC: Intel: bytcr_rt565: fix missing assignment to ret_val

Currently, the check that ret_val is not -ENOENT is always true and
the quirk bit BYT_RY5651_MCLK_EN is never being cleared because ret_val
is always zero at this point from a previous assignment earlier on.
I believe that ret_val should actually be assigned to the return from
devm_clk_get() as this can return -ENOENT (from a deeper call to
clk_get_sys) and that was the original intention to check this.

Detected by CoverityScan, CID#1460228 ("Logically dead code")

Fixes: 02c0a3b3

 ("ASoC: Intel: bytcr_rt5651: add MCLK, quirks and cleanups")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>