Fixed JAL instruction in corev-dv fence.i test

Created by: silabs-hfegran

JAL takes symbol, not a number-immediate. In the test, linker failures occurred in cases when the store fence.i exec stream randomization inserted a JAL instruction.

The instruction in question is supposed to never execute, so the jump symbol is set to be at the beginning of the stream, thus intentionally creating an infinite loop that will never be entered.

Additionally, compiler guards were added around the instructions that are being intentionally overwritten, to avoid potential problems with alignment and compressed instructions.

Signed-off-by: Henrik Fegran Henrik.Fegran@silabs.com