staging: mt7621-mmc: Fix power management by removing old api

The mmc_suspend|resume_host functions have been decrepated in the
3.11 [1] release and were completely removed in 3.13 [2]. Removing the
calls to this functions as it was done for other mmc host drivers
before the old api was removed (eg. [3]) fixes compile errors in this
driver while CONFIG_PM is enabled.

The rest of the removed code is simply dead, the MSDC_SYS_SUSPEND flag
is always set and will be removed in a later patch.

[1] commit 986892ca ("mmc: core: Initiate suspend|resume from mmc bus instead of mmc host")
[2] commit 3c0d22e8 ("mmc: core: Remove deprecated mmc_suspend|resume_host APIs")
[3] commit 1e63d485 ("mmc: au1xmmc: Move away from using deprecated APIs")

Signed-off-by: Christian Lütke-Stetzkamp <christian@lkamp.de>
Reviewed-by: NeilBrown <neil@brown.name>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>