mmc: tmio: remove outdated comment

mmc: tmio: remove outdated comment

The obviously wrong comment was added in 2011 with commit 28aab7c043a8c2
("mmc: protect the tmio_mmc driver against a theoretical race") but
already obsoleted half a year later with commit 3d72b161cfd58f ("mmc:
tmio: fix recursive spinlock, don't schedule with interrupts disabled").

Fixes: 3d72b161cfd58f ("mmc: tmio: fix recursive spinlock, don't schedule with interrupts disabled")
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>