.gitignore: Ignore .log files

The generated flash.log file that mach-imx uses for MKIMAGEOUTPUT is not
covered by any other ignore pattern. Ignore all *.log files.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
diff --git a/.gitignore b/.gitignore
index 3df3139..c2afcfb 100644
--- a/.gitignore
+++ b/.gitignore
@@ -41,6 +41,7 @@
 /System.map
 /u-boot*
 /boards.cfg
+/*.log
 
 #
 # git files that we don't want to ignore even it they are dot-files