.gitignore: Do not let git track '*.fd'

These files are usually binaries, and should never be committed.

Change-Id: I9df80f777020632e4c82a06ae3ae73c95234f3b5
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/46322
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

.gitignore

@@ -59,6 +59,7 @@ site-local
 *.debug
 !Kconfig.debug
 *.elf
+*.fd
 *.o
 *.o.d
 *.out