.gitignore: add .gcda files

These files contain the runtime coverage data generated by gcov.
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

.gitignore

@@ -24,6 +24,7 @@
 *.dwo
 *.elf
 *.gcno
+*.gcda
 *.gz
 *.i
 *.ko