manifest: upgrade hal_gigadevice revision

Upgrade hal_gigadevice to fetch the new features:
 - support gd32f4xx and gd32f3x0 series
 - pinctrl support for GD32F403, GD32F450, GD32VF103
 - Add README

Signed-off-by: HaiLong Yang <[email protected]>

Author: cameled

west.yml

@@ -73,7 +73,7 @@ manifest:
       groups:
         - hal
     - name: hal_gigadevice
-      revision: ce323de9655972a545cbdddda813c1576d85d5d1
+      revision: 749fdd4b9dc9dfc57daac1229a5a669109e14624
       path: modules/hal/gigadevice
       groups:
         - hal