google/veyron: Fix old style function definition

Function definitions without a type a deprecated in all versions of C.

Change-Id: I2efb42e653b0deb56ba6b0c9789764a9cabc552e
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/70138
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>
Reviewed-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/mainboard/google/veyron/bootblock.c b/src/mainboard/google/veyron/bootblock.c
index 0d11462..6b0cc81 100644
--- a/src/mainboard/google/veyron/bootblock.c
+++ b/src/mainboard/google/veyron/bootblock.c
@@ -14,7 +14,7 @@
 
 #include "board.h"
 
-void bootblock_mainboard_early_init()
+void bootblock_mainboard_early_init(void)
 {
 	if (CONFIG(CONSOLE_SERIAL)) {
 		assert(CONFIG_CONSOLE_SERIAL_UART_ADDRESS == UART2_BASE);
diff --git a/src/mainboard/google/veyron_mickey/bootblock.c b/src/mainboard/google/veyron_mickey/bootblock.c
index d9358a3..261d7e5 100644
--- a/src/mainboard/google/veyron_mickey/bootblock.c
+++ b/src/mainboard/google/veyron_mickey/bootblock.c
@@ -14,7 +14,7 @@
 
 #include "board.h"
 
-void bootblock_mainboard_early_init()
+void bootblock_mainboard_early_init(void)
 {
 	if (CONFIG(CONSOLE_SERIAL)) {
 		assert(CONFIG_CONSOLE_SERIAL_UART_ADDRESS == UART2_BASE);
diff --git a/src/mainboard/google/veyron_rialto/bootblock.c b/src/mainboard/google/veyron_rialto/bootblock.c
index 5230378..a0ce1ab 100644
--- a/src/mainboard/google/veyron_rialto/bootblock.c
+++ b/src/mainboard/google/veyron_rialto/bootblock.c
@@ -14,7 +14,7 @@
 
 #include "board.h"
 
-void bootblock_mainboard_early_init()
+void bootblock_mainboard_early_init(void)
 {
 	if (CONFIG(CONSOLE_SERIAL)) {
 		assert(CONFIG_CONSOLE_SERIAL_UART_ADDRESS == UART2_BASE);