clk: qcom: Add EBI2 clocks for IPQ806x

The NAND controller within EBI2 requires EBI2_CLK and
EBI2_ALWAYS_ON_CLK clocks.  Create structs for these clocks so
that they can be used by the NAND controller driver. Add an entry
for EBI2_AON_CLK in the gcc-ipq806x DT binding document.

Signed-off-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>