msm: camera: vfe: Update array size in bus read

This change will update the top irq register
mask array size to three as the total number
of top irq registers are three.

Change-Id: I556443932d81aa129c9f9600999e5886d2d5f92c
Signed-off-by: Vishalsingh Hajeri <vhajeri@codeaurora.org>