arm: exynos: arndale: Remove unused CONFIG_POWER and CONFIG_POWER_I2C

The CONFIG_POWER and CONFIG_POWER_I2C were introduced in
include/configs/exynos5-common.h in commit 19bd3aaa ("exynos5: fix
build break by adding CONFIG_POWER") and then it propagated up to
include/configs/arndale.h.  However before that commit, there was no
build break at all on Arndale and SMDK5250 boards.  It seems the commit
fixed nothing and just added unused defines.

In fact, the Arndale board is not configuring its PMIC (S5M8767) which
uses I2C bus.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>