arm: hw_breakpoint: squashed commits to enable HAVE_HW_BREAKPOINT

- taken from https://github.com/Kevindeving/kernel_lge_gee/commit/fa593b93462ff32b3d7988ffbcf79ef2ba799265

ARM: hw_breakpoint: enable HAVE_HW_BREAKPOINT feature flag
HAVE_HW_BREAKPOINT was disabled temporarily from commit
480a82f. Issue not seen with the
latest kernel hence re-enable the feature and fix merge issue from
previous kernel upgrade.

Change-Id: Ia6e7e8282c848dd73108e4d951b3375bb7caa63c
Signed-off-by: Jin Hong <jinh@codeaurora.org>
Signed-off-by: Taniya Das <tdas@codeaurora.org>

- taken from https://github.com/Kevindeving/kernel_lge_gee/commit/ad3c3e8f2ab4f8c5067a3cb1296866bfcc2bf45c

Add a missing variable definition

- thanks to Kevindeving and mathkid95