clk: fsl-sai: Extract clock setup into fsl_sai_clk_register()

clk: fsl-sai: Extract clock setup into fsl_sai_clk_register()

Create helper function fsl_sai_clk_register() to set up and register
SAI clock. Rename BCLK specific struct fsl_sai_clk members with bclk_
prefix. Use of_node_full_name(dev->of_node) and clock name to register
uniquely named clock. This is done in preparation for the follow up
patch, which adds MCLK support.

Signed-off-by: Marek Vasut <marex@nabladev.com>
Reviewed-by: Brian Masney <bmasney@redhat.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>