Fixed dependency between Zc and Zbb
Created by: Silabs-ArjanB
Fix related to https://github.com/riscv/riscv-code-size-reduction/issues/159 Introduced B_EXT = ZBA_ZBB option as well (did not optimize for area yet; will file ticket for that) SEC clean with Zc = 0.
Signed-off-by: Arjan Bink Arjan.Bink@silabs.com