clk: renesas: r7s9210: Always use readl()

On arm32, there is no reason to use the (soon deprecated) clk_readl().
Hence use the generic readl() instead.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>