Not all clocks are implemented but client drivers can still
request them. Currently we will return a NULL pointer to them if
the clock isn't implemented in software but NULL pointers are
valid clock pointers. Return an error pointer so that driver's
don't proceed without a clock they may actually need.
Signed-off-by: NStephen Boyd <sboyd@codeaurora.org>
Signed-off-by: NMike Turquette <mturquette@linaro.org>

Most of the probe code is the same between all the different
clock controllers. Consolidate the code into a common.c file.
This makes changes to the common probe parts easier and reduces
chances for bugs.
Signed-off-by: NStephen Boyd <sboyd@codeaurora.org>
Signed-off-by: NMike Turquette <mturquette@linaro.org>