part:efi: Move part_efi.h file to ./include

This move is necessary to export gpt header and GPT partition entries to be
used with other commands or subsystems.
Additionally the part_efi.h file has been cleaned-up to supress checkpatch's
warnings.

Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>