init: Replace simple_strtoul() with kstrtouint() in root_delay_setup()

init: Replace simple_strtoul() with kstrtouint() in root_delay_setup()

Replace deprecated simple_strtoul() with kstrtouint() for better error
handling and input validation. Return 0 on parsing failure to indicate
invalid parameter, maintaining existing behavior for valid inputs.

The simple_strtoul() function is deprecated in favor of kstrtoint()
family functions which provide better error handling and are recommended
for new code and replacements.

Signed-off-by: Kaushlendra Kumar <kaushlendra.kumar@intel.com>
Link: https://patch.msgid.link/20251103080627.1844645-1-kaushlendra.kumar@intel.com
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>