drivers/iio/adc/cf_axi_jesd204b_gt: Fix clock propagation (FMCDAQ2)

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
arch/microblaze/boot/dts/vc707_fmcadc5.dts: Add JESD/GT name index

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>