Revert "ANDROID: arm64: debug-monitors: export break hook APIs"

This reverts commit 210d9157.

Well, most of that commit, all except the register_kernel_break_hook
export, as that was actually being used.  All of the other symbol
exports were not being used at all, so they did not need to be exported.

Bug: 169899018
Bug: 157965270
Cc: Jonglin Lee <jonglin@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: Ib00df5822901ed81f4ec5147e63e37589eeee793