cpufreq: s3c24xx: rename CONFIG_CPU_FREQ_S3C24XX_DEBUGFS

The Kconfig symbol CPU_FREQ_S3C24XX_DEBUGFS was renamed to
ARM_S3C24XX_CPUFREQ_DEBUGFS in commit f023f8dd ("cpufreq: s3c24xx:
move cpufreq driver to drivers/cpufreq"). But that commit missed one
instance of its macro CONFIG_CPU_FREQ_S3C24XX_DEBUGFS. Rename it too.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>