mmc: mmc_spi: Simplify busy loop in mmc_spi_skip()

mmc: mmc_spi: Simplify busy loop in mmc_spi_skip()

Infinite loops are hard to read and understand because of
hidden main loop condition. Simplify such one in mmc_spi_skip().

Using schedule() to schedule (and be friendly to others)
is discouraged and cond_resched() should be used instead.
Hence, replace schedule() with cond_resched() at the same
time.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20210623101731.87885-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>