s5p: cpu_info: print "cpu-model" if exists in dts

s5p: cpu_info: print "cpu-model" if exists in dts

The CPU name for Exynos was concatenated with cpu id,
but for new Exynos platforms, like Chromebook Peach Pi
based on Exynos5800, the name of SoC variant does not
include the real SoC cpu id (0x5422).

For such case, the CPU name should be defined in device tree.

This commit introduces new device-tree property for Exynos:
- "cpu-model" - with cpu name string
If defined, then the cpu id is not printed.

Signed-off-by: Przemyslaw Marczak <p.marczak@samsung.com>
Cc: Minkyu Kang <mk7.kang@samsung.com>
Cc: Simon Glass <sjg@chromium.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Anand Moon <linux.amoon@gmail.com>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>