Like mentioned in the coment we need the size of the entire flash chip.
Check if a master exists and take his size.
Otherwise the limit will be too small and kernel prints:
UBI warning: print_rsvd_warning: cannot reserve enough PEBs for \
bad PEB handling, reserved 19, need 20
Signed-off-by: Jan Weitzel <j.weitzel@phytec.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>