ubifs-utils: Add implementations for linux kernel printing functions

ubifs-utils: Add implementations for linux kernel printing functions

Add implementations for linux kernel printing functions, because these
functions(eg. pr_debug, pr_err, etc.) are widely used in UBIFS linux
kernel libs. No need to define multiple levels in dbg_msg for debuging,
just replace dbg_msg with pr_debug. Now, there are five levels of
printing messages:
 0 - none
 1 - error message
 2 - warning message [default]
 3 - notice message
 4 - debug message

This is a preparation for replacing implementation of UBIFS utils with
linux kernel libs.

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