build-sys: Add spiceqxl_smartcard.h to _SOURCES
build-sys: Add spiceqxl_smartcard.h to _SOURCES

This file needs to be listed in Makefile.am otherwise it will not be
added to the tarballs make dist generates.

fgouget/xf86-video-qxl,fgouget/xf86-video-qxl,fgouget/xf86-video-qxl,fgouget/xf86-video-qxl