mmc: sdhci-msm: Fix error handling for dev_pm_opp_of_add_table()

Even though specifying OPP's in device tree is optional, ignoring all errors
reported by dev_pm_opp_of_add_table() means we can't distinguish between a
missing OPP table and a wrong/buggy OPP table. While missing OPP table
(dev_pm_opp_of_add_table() returns a -ENODEV in such case) can be ignored,
a wrong/buggy OPP table in device tree should make the driver error out.

while we fix that, lets also fix the variable names for opp/opp_table to
avoid confusion and name them opp_table/has_opp_table instead.

Suggested-by: Matthias Kaehlcke <matthias@chromium.org>
Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
Link: https://lore.kernel.org/r/1588080785-6812-10-git-send-email-rnayak@codeaurora.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>