arm: dts: mvebu: Update DTS for Thecus N2350 board

- Change the spi-max-frequency to 50000000 (50 Mhz). According to the
data sheet[1], the MX25L3205D max frequency is 86 Mhz. Using 50 Mhz in
the DTS to ensure u-boot is consistent with what Linux kernel expected.
- Update GPIO fan to conform to the latest DT binding.

[1]
https://www.macronix.com/Lists/Datasheet/Attachments/8575/MX25L3205D,%203V,%2032Mb,%20v1.5.pdf

Signed-off-by: Tony Dinh <mibodhi@gmail.com>
1 file changed