esp_system: create ld template to abstract few common settings

PMS aware chips require prefetch padding size for instruction fetch, or
some memory alignment considerations. These settings are now exposed
through kconfig options (hidden) and used through common ld template.
This shall help to add and manage future chips support easily for
these considerations.

Closes IDF-3624

components/esp_system/ld/esp32/memory.ld.in

@@ -20,6 +20,7 @@
    to simple macros with numeric values, and/or #if/#endif blocks.
 */
 #include "sdkconfig.h"
+#include "ld.common"
 
 /* If BT is not built at all */
 #ifndef CONFIG_BT_RESERVE_DRAM

components/esp_system/ld/esp32/sections.ld.in

@@ -349,7 +349,7 @@ SECTIONS
       * safe access to up to 16 bytes after the last real instruction, add
       * dummy bytes to ensure this
       */
-    . += 16;
+    . += _esp_flash_mmap_prefetch_pad_size;
 
     _text_end = ABSOLUTE(.);
     _etext = .;