msm: camera: Remove is-vpe property from device tree

is-vpe property is obsolete. Remove it from device tree and
associated code in msm_sensor to read and interpret its value

Change-Id: I2428bbd34c784ef23aed2c0051dcaf511d3f3c3b
Signed-off-by: Sreesudhan Ramakrish Ramkumar <srramku@codeaurora.org>