drivers/ipmi: Change type of custom_count from int to size_t

The variable `custom_count` is the number of custom fields, so only
holds non-negative values, so change the struct member type from int to
size_t.

Change-Id: Ic35aafefc870092298523ba2e10adf4fcb687a01
Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/60790
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/drivers/ipmi/ipmi_ops.h b/src/drivers/ipmi/ipmi_ops.h
index 60983b4..d900272 100644
--- a/src/drivers/ipmi/ipmi_ops.h
+++ b/src/drivers/ipmi/ipmi_ops.h
@@ -111,7 +111,7 @@
 	char *asset_tag;
 	char *fru_file_id;
 	char **product_custom;
-	int custom_count; /* Number of custom fields */
+	size_t custom_count; /* Number of custom fields */
 };
 
 struct fru_board_info {
@@ -121,7 +121,7 @@
 	char *part_number;
 	char *fru_file_id;
 	char **board_custom;
-	int custom_count;
+	size_t custom_count;
 };
 
 struct fru_chassis_info {
@@ -129,7 +129,7 @@
 	char *chassis_partnumber;
 	char *serial_number;
 	char **chassis_custom;
-	int custom_count;
+	size_t custom_count;
 };
 
 struct fru_info_str {