src/arch/x86/acpigen: Compare dev_states_count to size_t

Spotted out using -Wconversion gcc warning option.

Change-Id: Ib882cfa6d429fbfcab2b8132280182b427d510aa
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/33803
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/arch/x86/acpigen.c b/src/arch/x86/acpigen.c
index 74cd25a..f9af102 100644
--- a/src/arch/x86/acpigen.c
+++ b/src/arch/x86/acpigen.c
@@ -1115,7 +1115,7 @@
 void acpigen_write_power_res(const char *name, uint8_t level, uint16_t order,
 			     const char *dev_states[], size_t dev_states_count)
 {
-	int i;
+	size_t i;
 	for (i = 0; i < dev_states_count; i++) {
 		acpigen_write_name(dev_states[i]);
 		acpigen_write_package(1);