efi: Reworked EFI boot loader on several fronts.

efi: Reworked EFI boot loader on several fronts.

a) Added EFI timer handling in support of menu subsystem. This enables
the menu system to display and handle timeout properly.

b) Taking the cue from http://git.kernel.org/?p=boot/efilinux/efilinux.git
on the requirement that key kernel data structures need to be capped
at 0x3FFFFFFF, reworked the efi boot loader accordingly. The patch for the
boot loader is an adapted from the recent patches in efilinux as noted
above.

c) Arrow keys (up/down) in the menu system were not working earlier
requiring the user to use CTRL sequence keys instead. Implemented fixes to map
the EFI scan code to appropriate key sequences in order for get_key()
to handle the menu traversal in a user-friendly fashion.

d)efi/keymap.h has been added in support of key scan code mapping.

Signed-off-by: Chandramouli Narayanan <chandramouli.narayanan@intel.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>