[ARM] arm32ve: Implement arch_delay_loop_cycles() in assembly

The delay loop count to machine cycle count conversion for
Cortex-A7 is very different from Cortex-A15 (emulated by
ARM Fast Models) hence we implement arch_delay_loop_cycles()
in assembly so that we can incorporate CPU specific calculation
for Cortex-A7.

Signed-off-by: Anup Patel <anup@brainfault.org>