Use the common path access functions. In order to simplify chcpu also implement
and use path_writestr() which writes a string to the path specified.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
A couple of these functions already have been copied to chcpu.c,
so it makes sense to move these functions into an own file.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>