devices:epiphany:loader: Use symbols instead of hardcoded addresses
devices:epiphany:loader: Use symbols instead of hardcoded addresses

Look up addresses in elf file by symbol rather than using hardcoded
values.

Signed-off-by: Ola Jeppsson <793f970c52ded1276b9264c742f19d1888cbaf73@adapteva.com>

aolofsson/pal,aolofsson/pal,mateunho/pal,mateunho/pal,eliteraspberries/pal,eliteraspberries/pal,mateunho/pal,eliteraspberries/pal,eliteraspberries/pal,parallella/pal,parallella/pal,aolofsson/pal,parallella/pal,eliteraspberries/pal,mateunho/pal,aolofsson/pal,parallella/pal,parallella/pal,mateunho/pal