mmc: goldfish: emulated MMC device

This driver handles the virtual MMC device present in the Goldfish emulator.
The patch folds together initial work from Mike Lockwood and patches by
San Mehat, Jun Nakajima and Tom Keel <thomas.keel@intel.com> plus cleanups
by Alan Cox to get it all into 3.6 shape.

Signed-off-by: Mike A. Chan <mikechan@google.com>
[cleaned up and x86 support added]
Signed-off-by: Sheng Yang <sheng@linux.intel.com>
Signed-off-by: Yunhong Jiang <yunhong.jiang@intel.com>
Signed-off-by: Xiaohui Xin <xiaohui.xin@intel.com>
Signed-off-by: Jun Nakajima <jun.nakajima@intel.com>
Signed-off-by: Bruce Beare <bruce.j.beare@intel.com>
[Moved to 3.4]
Signed-off-by: Tom Keel <thomas.keel@intel.com>
[Moved to 3.7]
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Chris Ball <cjb@laptop.org>