hw/arm/integratorcp: Support specifying features via -cpu

Since the integratorcp board creates the CPU object directly
rather than via cpu_arm_init(), we have to call the CPU
class parse_features() method ourselves if we want to
support the user passing features via the -cpu command
line argument as well as just the cpu name. Do so.

Signed-off-by: Julian Brown <julian@codesourcery.com>
[PMM: split out into its own patch]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>