configure.ac: move require_dri_shared_libs_and_glapi() before its users

configure.ac: move require_dri_shared_libs_and_glapi() before its users

Otherwise we'll get a lovely message as below:
"require_dri_shared_libs_and_glapi: command not found"

Cc: Steven Newbury <steve@snewbury.org.uk>
Reported-by: Steven Newbury <steve@snewbury.org.uk>
Fixes: da410e6afad "configure: explicitly require shared glapi for
enable-dri"
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Tested-by: Steven Newbury <steve@snewbury.org.uk>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>