ide: Fix pointer arithmetic in hpt3xx driver code (3rd try)

git commit 74811f35

 causes crash at
module load (or boot) time on my machine with a hpt374 controller.
The reason for this is that for initializing second controller which sets
(hwif->dev == host->dev[1]) to true (1), adds 1 to a void ptr, which
advances it by one byte instead of advancing it by sizeof(hpt_info) bytes.
Because of this, all initialization functions get corrupted data in info
variable which causes a crash at boot time.

This patch fixes that and makes my machine boot again.

The card itself is a HPT374 raid conroller: Here is the lspci -v output:
03:06.0 RAID bus controller: HighPoint Technologies, Inc. HPT374 (rev
07)
        Subsystem: HighPoint Technologies, Inc. Unknown device 0001
        Flags: bus master, 66MHz, medium devsel, latency 120, IRQ 28
        I/O ports at 8000 [size=8]
        I/O ports at 7800 [size=4]
        I/O ports at 7400 [size=8]
        I/O ports at 7000 [size=4]
        I/O ports at 6800 [size=256]
        Expansion ROM at fe8e0000 [disabled] [size=128K]
        Capabilities: [60] Power Management version 2

03:06.1 RAID bus controller: HighPoint Technologies, Inc. HPT374 (rev
07)
        Subsystem: HighPoint Technologies, Inc. Unknown device 0001
        Flags: bus master, 66MHz, medium devsel, latency 120, IRQ 28
        I/O ports at 9800 [size=8]
        I/O ports at 9400 [size=4]
        I/O ports at 9000 [size=8]
        I/O ports at 8800 [size=4]
        I/O ports at 8400 [size=256]
        Capabilities: [60] Power Management version 2

Signed-off-by: Masoud Sharbiani <masouds@google.com>
Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
[bart: use dev_get_drvdata() per Sergei's suggestion]
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>