util/cbfstool/.gitignore: Add CSE tool executables

Commit 796aeeba96fc (util/cse_fpt: Add a new tool for managing Intel CSE
FPT binaries) and commit d7fb6a90e1d0 (util/cse_serger: Add a new tool
for stitching CSE components) add two utilities, and building cbfstool
also generates executables for them. When building cbfstool standalone,
these executables are placed in `util/cbfstool/`, and Git should never
track them.

Specify these executables' file names in .gitignore in order to prevent
unintentional inclusion of these files in commits, which is very likely
to happen when using `git add` on directories.

Change-Id: I285a4d7aeee642822eaae2eb69e5d52efb4bc8c0
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/59670
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/util/cbfstool/.gitignore b/util/cbfstool/.gitignore
index 2de3ccb..0470a45 100644
--- a/util/cbfstool/.gitignore
+++ b/util/cbfstool/.gitignore
@@ -1,5 +1,7 @@
 cbfs-compression-tool
 cbfstool
+cse_fpt
+cse_serger
 elogtool
 fmaptool
 ifittool