ubifs-utils: Define PROGRAM_NAME as variable

ubifs-utils: Define PROGRAM_NAME as variable

PROGRAM_NAME is defined as a const string "mkfs.ubifs", which won't be
suitable for fsck.ubifs. Add 'program_name' member in ubifs_info
structure, define PROGRAM_NAME as ubifs_info.program_name. Then, error
messages will display right program name if fsck.ubifs is supported.
Besides, add 'program_type' member in ubifs_info structure to identify
which current program type is, without comparing program name.

Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>