Staging: keucr: Move the declaration of variable ErrXDCode in smilsub.c

This patch moves the declaration of variable ErrXDCode to file smilsub.c
since this is the only file which uses it. Hence, it also removes extern
declaration from the header file smil.h and unnecessary declaration in
smilmain.c

Signed-off-by: Rashika Kheria <rashika.kheria@gmail.com>
Reviewed-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>