hw/arm/stellaris: mention the CPU type in the description

Many of the other machine types do and seeing as these are the only M
profile devices I thought this would be helpful.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
add xpsr to save_state_to_spsr()
.travis.yml: disable IRC notifications
.travis.yml: refactor build steps into script.