Please merge my PR about __PKHBT and __PKHTB in STM32CubeG4 package

[etheory]

Hi there ST!

Could you please merge my PR: https://github.com/STMicroelectronics/STM32CubeG4/pull/39

I noticed whilst working on some extremely high performance code using M4 intrinsics that rotates between AOS and SOA for computation using the __PKHBT and __PKHTB calls from CMSIS that the generated assembly looked totally wrong. Then I noticed that ST has modified the standard CMSIS cmsis_gcc.h header to remove the inline ASM definitions.

In my particular case my PR improved the runtime performance of my entire application by 6.53%, which is a HUGE performance improvement that is hard to ignore.

Thanks.

P.S. why was this change made in the first place? Genuinely curious?

[etheory]

I'm pretty amazed that you haven't merged this and closed it because your extremely old copy of CMSIS has this old header setup for __PKHBT and __PKHTB and you don't seem to be interested in having an even vaguely up to date CMSIS build. Could you PLEASE revisit this? It's really not that difficult.