ARM: imx: Update DDR frequency on i.MX8M Plus DHCOM

Commit 99c7cc58 ("ddr: imx: Add i.MX9 DDR controller driver")
contains an inobvious side-effect which renders all systems using
DRAM controller at 3732 MT/s unbootable. The change is located in
ddrphy_init_set_dfi_clk(), where the switch case statement entry
3732 changed to entry 3733, so any board with DDR calibration data
for 3732 MT/s operations needs to be updated to 3733 MT/s to match
the change.

Since there is currently only one such board, update the board instead
of handling both 3732 and 3733 options in the driver. It is likely the
NXP MX8MP RPA update will follow and use the later value too.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Fabio Estevam <festevam@denx.de>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Ye Li <ye.li@nxp.com>
Cc: uboot-imx <uboot-imx@nxp.com>
Reviewed-by: Fabio Estevam <festevam@denx.de>