ARM: OMAP5/DRA7: Enable iodelay recalibration to be done from uboot

Add a new API to perform iodelay recalibration without isolate
io to be used in uboot.

The data manual of J6/J6 Eco recommends to set different IODELAY values
depending on the mode in which the MMC/SD is enumerated in order to
ensure IO timings are met. The MMC driver can use the new API to
set the IO delay values depending on the MMC mode.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>