[PATCH] ahci: do not mangle saved HOST_CAP while resetting controller

Do not mangle with HOST_CAP while resetting controller.  The code is
there for a historical reason.  The mangling breaks controller feature
detection and 0 PORTS_IMPL workaround code.

This problem was spotted by Manoj Kasichainula.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Cc: Manoj Kasichainula <manoj@io.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>