sdhci-pltfm: switch to module device table matching

Sometimes want to place SoC-specific parts alongside with the generic
driver, and to do so, we have to switch the driver over to the module
device table matching.

Note that drivers/mmc/host/sdhci-pltfm.h is so far empty, but it'll hold
SoC-specific driver data handlers soon.

Signed-off-by: Anton Vorontsov <avorontsov@mvista.com>
Cc: Ben Dooks <ben@simtec.co.uk>
Cc: Richard R?jfors <richard.rojfors@pelagicore.com>
Cc: <linux-mmc@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>