spi: rzv2h-rspi: move register writes out of rzv2h_rspi_setup_clock()

spi: rzv2h-rspi: move register writes out of rzv2h_rspi_setup_clock()

In preparation for caching the last requested transfer frequency, move
register writes outside of rzv2h_rspi_setup_clock().

The transfer list is iterated to determine the speed of the transfer
and the bits per word.

The speed of the transfer is used to compute SPR and BRDV inside
rzv2h_rspi_setup_clock().

BRDV and SPB are stored in the SPCMD register.

Move the transfer iteration earlier, move the SPR and BRDV writing out
of rzv2h_rspi_setup_clock(), consolidate writing BRDV and SPB into the
initial write to the SPCMD register.

Signed-off-by: Cosmin Tanislav <cosmin-gabriel.tanislav.xa@renesas.com>
Link: https://patch.msgid.link/20251119161434.595677-5-cosmin-gabriel.tanislav.xa@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>