EDD: add edd=off and edd=skipmbr command line options
   
New command line options
edd=off     (or edd=of)
edd=skipmbr (or edd=sk)

runtime options for disabling all EDD int13 calls completely, or for
skipping the int13 READ SECTOR calls, respectively.

These are provided to allow Linux distributions to include CONFIG_EDD=m, yet
allow end-users to disable parts of EDD which may not work well with their
system's BIOS.

I incorporated comments from Randy Dunlap, and got an ack from Andi Kleen.
Signed-off-by: Matt Domsch <Matt_Domsch@dell.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>