added checking out a certain revision of linux-xlnx

recipes-kernel/linux/linux-xlnx_3.10.bbappend

@@ -11,10 +11,14 @@ SRCREV = "efc27505715e64526653f35274717c0fc56491e3"
 linux-elphel_label= "git://git.code.sf.net/p/elphel/linux-elphel"
 linux-elphel_branch= "master"
 linux-elphel_gitdir= "${WORKDIR}/linux-elphel"
+# To use the latest leave ""
+linux-elphel_srcrev= ""
+#linux-elphel_srcrev= "0ca36687a400fd9a5c4510295ae5be88aac77fa4"
 
 do_fetch_append() {
     print("Cloninig ${linux-elphel_label}\n")
     os.system("git clone -b ${linux-elphel_branch} ${linux-elphel_label} ${linux-elphel_gitdir}")
+    os.system("cd ${linux-elphel_gitdir};git checkout ${linux-elphel_srcrev}")
 }
 
 do_unpack_append() {