fs: zms: make zms_active_sector_free_space return type signed

zms_active_sector_free_space is documented to return -EACCES on fs not
mounted error but currently returns an usigned type size_t. This fixes
that by changing the return value into a ssize_t

Signed-off-by: Theis Mejnertsen <[email protected]>

Author: OmegaRelay

include/zephyr/fs/zms.h

@@ -218,7 +218,7 @@ ssize_t zms_calc_free_space(struct zms_fs *fs);
  * @retval >=0 Number of free bytes in the currently active sector
  * @retval -EACCES if ZMS is still not initialized.
  */
-size_t zms_active_sector_free_space(struct zms_fs *fs);
+ssize_t zms_active_sector_free_space(struct zms_fs *fs);
 
 /**
  * @brief Close the currently active sector and switch to the next one.

subsys/fs/zms/zms.c

@@ -1837,7 +1837,7 @@ ssize_t zms_calc_free_space(struct zms_fs *fs)
 	return free_space;
 }
 
-size_t zms_active_sector_free_space(struct zms_fs *fs)
+ssize_t zms_active_sector_free_space(struct zms_fs *fs)
 {
 	if (!fs->ready) {
 		LOG_ERR("ZMS not initialized");