tizen: enable support for formatting MBR partition layout during flashing

tizen: enable support for formatting MBR partition layout during flashing

This is ensured by the following steps:
1. enable 'mbr' command and provide default partiton layout,
2. add support for formating block device from THOR downloaded script,
3. check MBR partition layout on boot and enter THOR mode if invalid
4. provide a script for formating MBR for THOR download

MBR partition layout is checked on boot if it mathes the one defined
during u-boot compilation. If not, set dfu_alt_info to the minimal safe
list and enter THOR download mode to flash the new, proper partition
layout and the complete Tizen image.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Change-Id: I490e5b3314513012259f3981feae047f95649c3b