mmc: tmio: Replace msleep() of 20ms or less with usleep_range()

As documented in Documentation/timers/timers-howto.txt
as follows, replace msleep() with usleep_range().

msleep(1~20) may not do what the caller intends, and
will often sleep longer (~20 ms actual sleep for any
value given in the 1~20ms range). In many cases this
is not the desired behavior.

Signed-off-by: Masaharu Hayakawa <masaharu.hayakawa.ry@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Acked-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>