clk: sifive: Do not register clkdevs for PRCI clocks

These clkdevs were unnecessary, because systems using this driver always
look up clocks using the devicetree. And as Russell King points out[1],
since the provided device name was truncated, lookups via clkdev would
never match.

Recently, commit 8d532528 ("clkdev: report over-sized strings when
creating clkdev entries") caused clkdev registration to fail due to the
truncation, and this now prevents the driver from probing. Fix the
driver by removing the clkdev registration.

Link: https://lore.kernel.org/linux-clk/ZkfYqj+OcAxd9O2t@shell.armlinux.org.uk/ [1]
Fixes: 30b8e27e ("clk: sifive: add a driver for the SiFive FU540 PRCI IP block")
Fixes: 8d532528

 ("clkdev: report over-sized strings when creating clkdev entries")
Reported-by: Guenter Roeck <linux@roeck-us.net>
Closes: https://lore.kernel.org/linux-clk/7eda7621-0dde-4153-89e4-172e4c095d01@roeck-us.net/
Suggested-by: Russell King <linux@armlinux.org.uk>
Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
Link: https://lore.kernel.org/r/20240528001432.1200403-1-samuel.holland@sifive.com
Signed-off-by: Stephen Boyd <sboyd@kernel.org>