src/acpi/soundwire.c: Add missing <stddef.h>

size_t needs <stddef.h>. Replace unused <stdint.h> with <stddef.h>.

Change-Id: Ib9ab5555adeeddd9eea7a93dbb166d8479eca42e
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/43340
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/acpi/soundwire.c

@@ -6,7 +6,7 @@
 #include <commonlib/helpers.h>
 #include <device/soundwire.h>
 #include <stdbool.h>
-#include <stdint.h>
+#include <stddef.h>
 
 /* Specification-defined prefix for SoundWire properties. */
 #define SDW_PFX "mipi-sdw-"