This commit fixes Bug #528.
1. Added the target arch name to the pkg name of gcc-cross-canadian,
gdb-cross-candian and bintuils-cross-candian.
2. Move the cross-canadian pkgs out of task-sdk-host into a new task
task-cross-canadian.
3. Added the RDEPENDS of task-cross-canadian into meta-toolchain.
Signed-off-by: Lianhao Lu <lianhao.lu@intel.com>