clk: add new APIs to operate on all available clocks

This patch introduces of_clk_bulk_get_all and clk_bulk_x_all APIs
to users who just want to handle all available clocks from device tree
without need to know the detailed clock information likes clock numbers
and names. This is useful in writing some generic drivers to handle clock
part.

Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: Thor Thayer <thor.thayer@linux.intel.com>
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>