UPSTREAM: rtc: rtc-palmas: make of_device_id array const

(cherry pick from commit 7abe3f5404fae84cecd851e140a2218ba9d24e4f)

Make of_device_id array const, because all OF functions handle it as
const.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Bug: 26346842
Change-Id: I8bde243d8d8dcf7365cea06384cf40cab2406137