NFC: trf7970a: Set 'Modulator and SYS_CLK Control' after 'ISO Control'

Writing to the 'ISO Control' register may cause the contents of the
'Modulator and SYS_CLK Control' register to change so be sure to write
to 'Modulator and SYS_CLK Control' after writing to 'ISO Control'.

Note that writing to the 'Modulator and SYS_CLK Control' register
shouldn't be necessary at all according to the trf790a manual but testing
shows that it is necessary.

Signed-off-by: Mark A. Greer <mgreer@animalcreek.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>