libpayload: Fix untyped function arguments

This is necessary with clang.

Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Change-Id: Icc197fbd48b49bfa8770caf01727669b0ac59090
Reviewed-on: https://review.coreboot.org/c/coreboot/+/77433
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Elyes Haouas <ehaouas@noos.fr>

payloads/libpayload/libc/malloc.c

@@ -112,7 +112,7 @@ void init_dma_memory(void *start, u32 size)
 #endif
 }
 
-int dma_initialized()
+int dma_initialized(void)
 {
 	return dma != heap;
 }