fix(stm32mp1): rework DWL buffer cache invalidation

As the default part do nothing, all the code managing DWL buffer cache
invalidation can be under programmer flags.
This avoids running unneeded code if the flags are not enabled, and
corrects MISRA C2012-16.6:
Every switch statement shall have at least two switch-clauses.

Signed-off-by: Yann Gautier <>
Change-Id: I90d2951f9518509b3380295fb1a6ad6b9c5e551e
1 file changed