spi: spi-fsl-lpspi: Fix off-by-one in prescale max

The commit 783bf5d0 ("spi: spi-fsl-lpspi: limit PRESCALE bit in
TCR register") doesn't implement the prescaler maximum as intended.
The maximum allowed value for i.MX93 should be 1 and for i.MX7ULP
it should be 7. So this needs also a adjustment of the comparison
in the scldiv calculation.

Fixes: 783bf5d0 ("spi: spi-fsl-lpspi: limit PRESCALE bit in TCR register")
Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
Link: https://patch.msgid.link/20240905111537.90389-1-wahrenst@gmx.net


Signed-off-by: Mark Brown <broonie@kernel.org>