Move trailer status size calculation to its own function
diff --git a/boot/bootutil/src/bootutil_priv.h b/boot/bootutil/src/bootutil_priv.h
index 925e7f3..59f655d 100644
--- a/boot/bootutil/src/bootutil_priv.h
+++ b/boot/bootutil/src/bootutil_priv.h
@@ -99,6 +99,7 @@
uint8_t key_id);
uint32_t boot_slots_trailer_sz(uint8_t min_write_sz);
+int boot_status_entries(const struct flash_area *fap);
uint32_t boot_status_off(const struct flash_area *fap);
int boot_read_swap_state(const struct flash_area *fap,
struct boot_swap_state *state);