toolchain-external: bump Linaro ARMeb toolchain to 2014.04

For some reason, there is no ARMeb toolchain available in the 2014.05
Linaro release.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>