boot/zephyr: fix compilation errors in logging.

Both static `boot_image_validate_once()` functions in the Zephyr
application have a flash area parameter named `fa_p`, not `fap_p`. This
presumably went unnoticed because these functions are only compiled when
`MCUBOOT_VALIDATE_PRIMARY_SLOT_ONCE` is defined.

Signed-off-by: Samuel Coleman <samuel.coleman@rbr-global.com>

Author: rbrscoleman

boot/zephyr/firmware_loader.c

@@ -73,7 +73,7 @@ boot_image_validate_once(const struct flash_area *fa_p,
     int rc;
     FIH_DECLARE(fih_rc, FIH_FAILURE);
 
-    BOOT_LOG_DBG("boot_image_validate_once: flash area %p", fap_p);
+    BOOT_LOG_DBG("boot_image_validate_once: flash area %p", fa_p);
 
     memset(&state, 0, sizeof(struct boot_swap_state));
     rc = boot_read_swap_state(fa_p, &state);

boot/zephyr/single_loader.c

@@ -85,7 +85,7 @@ boot_image_validate_once(const struct flash_area *fa_p,
     int rc;
     FIH_DECLARE(fih_rc, FIH_FAILURE);
 
-    BOOT_LOG_DBG("boot_image_validate_once: flash area %p", fap_p);
+    BOOT_LOG_DBG("boot_image_validate_once: flash area %p", fa_p);
 
     memset(&state, 0, sizeof(struct boot_swap_state));
     rc = boot_read_swap_state(fa_p, &state);