target/arm_adi_v5: sync CSW and TAR cache on apreg write

target/arm_adi_v5: sync CSW and TAR cache on apreg write

When using apreg to change AP registers CSW or TAR we get internal
cached value not valid anymore.

Reuse the setup functions for CSW and TAR to write them.
Invalidate the cached value before the call to force the write, thus
keeping original apreg behaviour.

Change-Id: Ib14fafd5e584345de94f2e983de55406c588ac1c
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/4565
Tested-by: jenkins
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>