[SCSI] megaraid: fix sparse warnings

There's a zero day mistake in the megaraid driver in that the code that
obtains the version number does a >> 8 on a char quantity.  This >>8 causes a
sparse warning because it always produces zero.  Al Viro suggested these
shifts should be >> 4 thus treating the firmware version as a BCD quantity.
However, in the interests of safety we've elected to replace the >> 8
quantities with an explicit zero, thus quieting the sparse warning while
preserving the same (albeit incorrect) version number as had previously been
seen.

Signed-off-by: Adam Radford <aradford@gmail.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>