egl: fix _eglMatchDriver() return type

The one caller only ever checks if the return value is NULL or not, so
let's simplify the function by only returning that information.

Signed-off-by: Eric Engestrom <eric@engestrom.ch>
Reviewed-by: Marcin Ĺšlusarz <marcin.slusarz@intel.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6037>
diff --git a/src/egl/main/egldriver.h b/src/egl/main/egldriver.h
index 5139033..0d0f507 100644
--- a/src/egl/main/egldriver.h
+++ b/src/egl/main/egldriver.h
@@ -35,6 +35,7 @@
 #include "c99_compat.h"
 
 #include "egltypedefs.h"
+#include <stdbool.h>
 #include <stddef.h>
 
 
@@ -223,7 +224,7 @@
 };
 
 
-extern _EGLDriver *
+extern bool
 _eglMatchDriver(_EGLDisplay *disp);