src/mainboard: Use 'const' to set pnp_devfn_t statically

Change-Id: I50ac6914fadc02491df2eccb437eada89fd12b82
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/40272
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
diff --git a/src/mainboard/roda/rk886ex/early_init.c b/src/mainboard/roda/rk886ex/early_init.c
index fe61187..baa17d1 100644
--- a/src/mainboard/roda/rk886ex/early_init.c
+++ b/src/mainboard/roda/rk886ex/early_init.c
@@ -35,9 +35,7 @@
 
 void bootblock_mainboard_early_init(void)
 {
-	pnp_devfn_t dev;
-
-	dev = PNP_DEV(0x2e, 0x00);
+	const pnp_devfn_t dev = PNP_DEV(0x2e, 0x00);
 
 	pnp_enter_conf_state(dev);
 	pnp_write_config(dev, 0x01, 0x94); /* Extended Parport modes */