platform: prefix MODALIAS with "platform:"

Prefix platform modalias strings with "platform:", which
modprobe config to blacklist alias resolving if userspace
configures it.

Send uevents for all platform devices.

Add MODULE_ALIAS's to: pxa2xx_pcmcia, ds1742 and pcspkr to trigger
module autoloading by userspace.

  $ modinfo pcspkr
  alias:          platform:pcspkr
  license:        GPL
  description:    PC Speaker beeper driver
  ...

  $ modprobe -n -v platform:pcspkr
  insmod /lib/modules/2.6.23-rc3-g28e8351a-dirty/kernel/drivers/input/misc/pcspkr.ko

Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Cc: David Brownell <david-b@pacbell.net>
Cc: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>