staging: ks7010: create reg_status_type enum type

SDIO header currently defines unused constants READ_STATUS_BUSY and
WRITE_STATUS_IDLE. There are reciprocal constants that are used
READ_STATUS_IDLE and WRITE_STATUS_BUSY. We can roll these into a
single enumeration type and remove the two that are unused.

Add enumeration type containing IDLE/BUSY pair that are currently used
within the SDIO source. Change source to use new enum types.

Signed-off-by: Tobin C. Harding <me@tobin.cc>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>