mmc: core: bus:

mmc: core: bus:
     Fix mmc_bus_suspend and mmc_bus_resume panic kernel bug. Since pm notify call
chain fall into mmc subsystem, host controller driver may not register bus_ops indeed ,
actually it's optional for bus-level drivers to complete this hook pointer.

[   42.603423] Freezing user space processes ... (elapsed 0.008 seconds) done.
[   42.611886] Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.
[   42.614351] Unable to handle kernel NULL pointer dereference at virtual address 00000000
[   42.630102] pgd = c0004000
[   42.632816] [00000000] *pgd=00000000
[   42.636483] Internal error: Oops: 80000005 [#1] PREEMPT SMP ARM
....
[   43.426496] [<c045f788>] (mmc_bus_suspend+0x40/0x44) from [<c02e94dc>] (dpm_run_callback.isra.5+0x28/0x60)
[   43.436168] [<c02e94dc>] (dpm_run_callback.isra.5+0x28/0x60) from [<c02e9b78>] (__device_suspend+0x1e4/0x274)

mmc: core: rockchip:
     Tags rockchip eMMC controller's pm_caps with MMC_PM_IGNORE_PM_NOTIFY refered to commit 3549af216ba41d5bd70.
eMMC controller now only ack probe/shudown and remove event by poweroff notify. Otherwise, PM freezing will be disterbed
by emergancy I/O error from file system.

[   42.710633] PM: suspend entry 2013-01-21 09:54:47.245333254 UTC
[   42.710659] PM: Syncing filesystems ... done.
[   42.728095] mmc0: card 0001 removed
[   42.828461] EXT4-fs error (device mmcblk0p12): ext4_wait_block_bitmap:466:
		comm PackageManager: Cannot read block bitmap - block_group = 1, block_bitmap = 34
[   42.828653] EXT4-fs (mmcblk0p12): delayed block allocation failed for inode 647 at logical offset 0 with
		max blocks 30 with error -5
[   42.828689] EXT4-fs (mmcblk0p12): This should not happen!! Data will be lost
[   42.829227] Aborting journal on device mmcblk0p12-8.
[   42.829322] JBD2: Error -5 detected when updating journal superblock for mmcblk0p12-8.
[   42.829409] journal commit I/O error
[   42.829942] EXT4-fs (mmcblk0p12): previous I/O error to superblock detected
......
[   43.179043] Freezing user space processes ...
[   43.179519] active wakeup source: mmc0_detect

Signed-off-by: lintao <lintao@rock-chips.com>