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
IRAM section didn't contain sufficient padding for possible CPU instruction prefetch,
ie instruction fetch could happen in DRAM section which is prohibited by the Memprot module.
This is fixed by adding 16B to the end of IRAM section in LD script (C3 CPU prefetch buffer depth is 4 words)
Closes IDF-3554
* fix
