mmc: tegra: add pm_flags

Enable fast bcm4329 WIFI suspend/resume on Tegra2 board.

This patch allows the mach-tegra support to tell the tegra MMC host
controller to NOT turn off power for the MMC controller the WIFI part
lives behind.  Thus bcm4329 firmware doesn't need to be reloaded.

Signed-off-by: Venkat Rao <vrao@broadcom.com>
Tested-by: Grant Grundler <grundler@chromium.org>
Reviewed-by: Olof Johansson <olof@lixom.net>
Acked-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Chris Ball <cjb@laptop.org>