drm/i915: Update SKL SRV GT4 pci ids reference.

No functional changes. Apparently spec has been changed
the valid table showing 0x192A as Server GT4
while 0x193A is Server GT4e.

Libdrm and Mesa already have this right. So let's fix the ref here.

Cc: Ben Widawsky <benjamin.widawsky@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Ben Widawsky <benjamin.widawsky@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1483471672-10450-1-git-send-email-rodrigo.vivi@intel.com