arm64: dts: st: Fix SAI addresses on stm32mp251

The second field of SAI register addresses should be within 0x3f0 bytes
from the start of the SAI register addresses, the second field describes
the ID registers which are at that addrses. Currently, the second field
does not match RM, fix it.

Fixes: bf26d75a95f1 ("arm64: dts: st: add sai support on stm32mp251")
Signed-off-by: Marek Vasut <marex@nabladev.com>
Reviewed-by: Olivier Moysan <olivier.moysan@foss.st.com>
Link: https://lore.kernel.org/r/20260411130300.19603-1-marex@nabladev.com
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>