bootloader_support: fix issue in memory mapping for getting app descriptor

For getting secure_version field in anti rollback case, bootloader tries
to map whole firmware partition but fails for cases where partition size
is beyond available MMU free pages capacity.

Fix here insures to map only required length upto application descriptor
size in firmware partition.

Closes https://github.com/espressif/esp-idf/issues/5911

components/bootloader_support/src/bootloader_common.c

@@ -183,13 +183,15 @@ esp_err_t bootloader_common_get_partition_description(const esp_partition_pos_t
         return ESP_ERR_INVALID_ARG;
     }
 
-    const uint8_t *image = bootloader_mmap(partition->offset, partition->size);
+    const uint32_t app_desc_offset = sizeof(esp_image_header_t) + sizeof(esp_image_segment_header_t);
+    const uint32_t mmap_size = app_desc_offset + sizeof(esp_app_desc_t);
+    const uint8_t *image = bootloader_mmap(partition->offset, mmap_size);
     if (image == NULL) {
-        ESP_LOGE(TAG, "bootloader_mmap(0x%x, 0x%x) failed", partition->offset, partition->size);
+        ESP_LOGE(TAG, "bootloader_mmap(0x%x, 0x%x) failed", partition->offset, mmap_size);
         return ESP_FAIL;
     }
 
-    memcpy(app_desc, image + sizeof(esp_image_header_t) + sizeof(esp_image_segment_header_t), sizeof(esp_app_desc_t));
+    memcpy(app_desc, image + app_desc_offset, sizeof(esp_app_desc_t));
     bootloader_munmap(image);
 
     if (app_desc->magic_word != ESP_APP_DESC_MAGIC_WORD) {