staging: mt7621-mmc: Remove unused functions

The functions msdc_eirq_cd and msdc_eirq_sdio are defined but never
used, so they are removed. This also fixes two compiler warnings:

drivers/staging/mt7621-mmc/sd.c:517:13: warning: ‘msdc_eirq_cd’ defined but
not used [-Wunused-function]
 static void msdc_eirq_cd(void *data)
             ^~~~~~~~~~~~
drivers/staging/mt7621-mmc/sd.c:507:13: warning: ‘msdc_eirq_sdio’ defined but
not used [-Wunused-function]
 static void msdc_eirq_sdio(void *data)

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