[U-Boot] test HYP mode in arch/arm/cpu/armv7/start.S

[TigerLiu at viatech.com.cn]

Hi, experts:
I found it would determine whether CPU was in HYP mode or not before
switching to SVC mode in reset handler.

So, why need to test HYP mode?
So, which case could cause CPU in HYP mode during U-Boot boot stage?

Best wishes,