ima: Fix fall-through warnings for Clang

[ Upstream commit 28073eb09c5aa29e879490edb88cfd3e7073821e ]

In preparation to enable -Wimplicit-fallthrough for Clang, fix multiple
warnings by explicitly adding multiple break statements instead of just
letting the code fall through to the next case.

Link: https://github.com/KSPP/linux/issues/115


Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Stable-dep-of: c7423dbdbc9e ("ima: Handle -ESTALE returned by ima_filter_rule_match()")
Signed-off-by: Sasha Levin <sashal@kernel.org>