ARM: EXYNOS: Add exynos3250 compatible to use generic cpufreq driver

This patch add exynos3250 compatible string to exynos_cpufreq_matches
for supporting generic cpufreq driver on Exynos3250.

Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Reviewed-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Kukjin Kim <kgene@kernel.org>