clk: bcm: rpi: Add NULL check in raspberrypi_clk_register()

clk: bcm: rpi: Add NULL check in raspberrypi_clk_register()

devm_kasprintf() returns NULL when memory allocation fails. Currently,
raspberrypi_clk_register() does not check for this case, which results
in a NULL pointer dereference.

Add NULL check after devm_kasprintf() to prevent this issue.

Fixes: 93d2725affd6 ("clk: bcm: rpi: Discover the firmware clocks")
Signed-off-by: Henry Martin <bsdhenrymartin@gmail.com>
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://lore.kernel.org/r/20250402020513.42628-1-bsdhenrymartin@gmail.com
Reviewed-by: Stefan Wahren <wahrenst@gmx.net>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>