mmc: fsl_esdhc: Gracefully fail on unsupported voltage switch

Unsupported voltage on voltage switch is not an error, do not
print error message in such a case. This happens e.g. if the
eMMC is already in 1V8 mode or when testing 1V2 mode operation
on systems which only do 3V3/1V8 switching.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Cc: Jaehoon Chung <jh80.chung@samsung.com>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>