mmc: sdhci: Update the tuning failed messages to pr_debug level

Tuning support in DDR50 speed mode was added in SD Specifications Part1
Physical Layer Specification v3.01. Its not possible to distinguish
between v3.00 and v3.01 from the SCR and that is why since
commit 4324f6de

 ("mmc: core: enable CMD19 tuning for DDR50 mode")
tuning failures are ignored in DDR50 speed mode.

Cards compatible with v3.00 don't respond to CMD19 in DDR50 and this
error gets printed during enumeration and also if retune is triggered at
any time during operation. Update the printk level to pr_debug so that
these errors don't lead to false error reports.

Signed-off-by: Faiz Abbas <faiz_abbas@ti.com>
Cc: stable@vger.kernel.org # v4.4+
Link: https://lore.kernel.org/r/20191206114326.15856-1-faiz_abbas@ti.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>