Add MMC5 support on BLAZE, which has the wl1283 device hardwired to.

The wl1283 is a 4-wire, 1.8V, embedded SDIO WLAN device with an external IRQ line,
and power-controlled by a GPIO-based fixed regulator.

Based on the patch for zoom by Ohad Ben-Cohen <ohad@wizery.com>
Signed-off-by: NVishal Mahaveer <vishalm@ti.com>
[tony@atomide.com: improved formatting a bit]
Signed-off-by: NTony Lindgren <tony@atomide.com>