YAFFS2: fs/yaffs2/yaffscfg.c - fix build warnings

Fix these:
yaffscfg.c: In function 'cmd_yaffs_mread_file':
yaffscfg.c:316: warning: format '%08x' expects type 'unsigned int', but argument 3 has type 'char *'
yaffscfg.c: In function 'cmd_yaffs_ls': yaffscfg.c:371: warning: format '%7d' expects type 'int', but argument 3 has type 'off_t'

Signed-off-by: Wolfgang Denk <wd@denx.de>