[ARM] orion/kirkwood: reset PCIe unit on boot

Patch found in QNAPs vendor source package, with some cleanups
(proper defines, shortened max. timeout from 1s to 200ms).

Without this patch the PCIe SATA controller (Marvell 88sx7042/sata_mv)
in my QNAP TS-419P (Marvell 88f6281/Kirkwood) stops working after a
few minutes.

The symptomes are described in this thread:
http://marc.info/?l=linux-ide&m=124822863706181&w=2

[ Note: this is a workaround in need of a better analysis/solution -- NP ]

Acked-by: Saeed Bishara <saeed@marvell.com>
Tested-by: Bernhard R. Link <brl@pcpool00.mathematik.uni-freiburg.de>
Seconded-by: Martin Michlmayr <tbm@cyrius.com>
I'm_not_very_happy_with_it-by: Lennert Buytenhek <buytenh@wantstofly.org>
Signed-off-by: Nicolas Pitre <nico@fluxnic.net>