clk: versatile: add min/max rate boundaries for vexpress osc clock

Clock framework has a provider API(clk_hw_set_rate_range) to set the
min/max rate of a clock. Use the same to set the boundaries for the
vexpress osc clock.

Cc: Michael Turquette <mturquette@baylibre.com>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: linux-clk@vger.kernel.org
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>