regulator: smd: Add floor and corner operations

This patch addes the Qualcomm specific functions for setting the floor and
corner voltages on the regulators.

Signed-off-by: Andy Gross <agross@codeaurora.org>
[georgi.djakov@linaro.org: Make work with struct regulator]
Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>