[rtl/controller] Remove redundant check in execption handling
[rtl/controller] Remove redundant check in execption handling

This commit turns the last case in the exception handling if/else block
from an `else if` to an `else`. This is not changing functional
behavior as the same condition is checked previously, but removes a
`MISSING_ELSE` coverage hole reported by @udinator.

Signed-off-by: Pirmin Vogel <386a7fc8e7338ed7899b4d9883c0ebec5de81366@lowrisc.org>

AmbiML/ibex,lowRISC/ibex,AmbiML/ibex,AmbiML/ibex,lowRISC/ibex,AmbiML/ibex,lowRISC/ibex,lowRISC/ibex