UBIFS: Missing offset relocation for compressor 'none'

On systems where U-Boot is linked to another address than it really lays
(e.g. backup image), calls via function pointers must be fixed with a
'+= gd->reloc_off'.
This was not done for none_compr in ubifs_compressors_init() what leads
to system crash on ubifsmount command.

Signed-off-by: Michael Lawnick <ml.lawnick@gmx.de>
Acked-by: Stefan Roese <sr@denx.de>