drivers: input: add general hall sensor driver

This change adds general hall sensor driver.

This snapshot is taken as of msm-3.10 'commit 1227f5746677 ("soc:
qcom: smp2p: spinlock_test: Initialize work item")' with minor
errors fixed.

Change-Id: Icd048fea42facca48b5d6b387218d6847f730d58
Signed-off-by: Bingzhe Cai <bingzhec@codeaurora.org>