clk: exynos5420: Add IDs for clocks used in PD mfc

Adds IDs for MUX clocks to be used by power domain for MFC
for doing re-parenting while pd on/off.

Signed-off-by: Arun Kumar K <arun.kk@samsung.com>
Signed-off-by: Shaik Ameer Basha <shaik.ameer@samsung.com>
Acked-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>