ARM: OMAP4: CPUidle: Make C-state description field more precise

It is useful to know the CPU power state along with MPUSS power state
in a supported C-state. Since the data is available via sysfs, one can
avoid scrolling the source code for precise construction of C-state.

Reported-by: Nishanth Menon <nm@ti.com>
Acked-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Kevin Hilman <khilman@linaro.org>