soc: samsung: Add exynos chipid driver support

Exynos SoCs have Chipid, for identification of product IDs and SoC
revisions. This patch intends to provide initialization code for all
these functionalities, at the same time it provides some sysfs entries
for accessing these information to user-space.

This driver uses existing binding for exynos-chipid.

Changes by Bartlomiej:
- fixed return values on errors
- removed bogus kfree_const()
- added missing Exynos4210 EVT0 id
- converted code to use EXYNOS_MASK define
- fixed np use after of_node_put()
- fixed too early use of dev_info()
- made driver fail for unknown SoC-s
- added SPDX tag
- updated Copyrights

Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.com>
[m.szyprowski: for suggestion and code snippet of product_id_to_soc_id]
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
[s.nawrocki: updated copyright date, removed uneeded headers inclusion]
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>