Changeset 870ff8e9 in rtems for c/src/lib/libbsp/arm/tms570/irq

bsp/tms570: use POM only when application image does not start at address 0.

Parameters overlay module is initialized and cleared first.
It is used later to replace exception target vectors
only if that is required.

The application loader code with CPU and SDRAM setup
code has to provide well defined pattern of instructions
at addresses 0x00000000 and 0x0000001f, because only data
read accesses can be processed reliably by POM. The expected
instruction pattern can be seen in the next example

​https://github.com/hornmich/tms570ls3137-hdk-sdram/blob/master/SDRAM_SCI_configuration/source/sys_intvecs.asm

Comments with detailed description of code, background
and reasons for selected approach have been included
in TMS570 bsp startup code.

Signed-off-by: Pavel Pisa <pisa@…>
Signed-off-by: Premysl Houdek <kom541000@…>