wl12xx: use the same plat dev name for both SPI and SDIO

There's no need to have the bus name included in the platform device
name that we create.  The core driver doesn't need to know about the
type of bus it uses.  Any differences between the buses that need to
be handled differently in the core, can be passed in the platform data
(as the pwr_in_suspend boolean does).

Use "wl12xx" for the device name in both bus drivers.  Rename the
platform driver name to "wl12xx_driver", just to differentiate from
the platform device names.

Signed-off-by: Luciano Coelho <coelho@ti.com>