clk: keystone: syscon-clk: fix regmap leak on probe failure

clk: keystone: syscon-clk: fix regmap leak on probe failure

The mmio regmap allocated during probe is never freed.

Switch to using the device managed allocator so that the regmap is
released on probe failures (e.g. probe deferral) and on driver unbind.

Fixes: a250cd4c1901 ("clk: keystone: syscon-clk: Do not use syscon helper to build regmap")
Cc: stable@vger.kernel.org	# 6.15
Cc: Andrew Davis <afd@ti.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>