mmc: TMIO: Fix I/O mapping leak on error using devm_ioremap()

Signed-off-by: Ian Molton <ian.molton@codethink.co.uk>
[bwh: Forward-ported to 4.0]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>