staging/comedi/me4000: fix sparse warning "obsolete struct initializer"

This patch fixes the sparse warnings in me4000.c:
me4000.c:122:1: warning: obsolete struct initializer, use C99 syntax
me4000.c:123:1: warning: obsolete struct initializer, use C99 syntax
me4000.c:124:1: warning: obsolete struct initializer, use C99 syntax
me4000.c:125:1: warning: obsolete struct initializer, use C99 syntax
by converting the struct to use C99 syntax

Signed-off-by: Peter Huewe <peterhuewe@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>