mmc: update to latest gingerbread_rel revision

The Samsung source is based on CodeAurora tag M76XXTSNCJNLYA6140,
which is missing several important updates to the MMC drivers
required for wifi stability.

Taken from revision: 7b8b192bb2cee24d4c932d5fc1a386e7da6ce435

Note: completely untouched (i.e. Samsung hacks removed). Separate
commit will re-add needed code to improve ar6003 compatibility.

Change-Id: Iadff5c4551507a5389803de12f0e02c356601158
(cherry picked from commit e18149f0e5168893fc2e21f8c21922c81398a13c)