ARM: S3C2440: CPUFREQ: Add crystal frequency Kconfig entries.

Add entries to select the crystal to select for each different
supported board. This information is then available for anything
else requiring this, such as the CPUFreq PLL tables.

Signed-off-by: Ben Dooks <ben@simtec.co.uk>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>