Update lpddr4_timing and blobs from upstream
These changes ensure that the reform u-boot fork works fine on nitrogen8m_som production runs / revisions that use a slightly different ram chip.
lddr4_timing_8mq.c
and ldddr_timing_ch2.h
both come from here: https://github.com/boundarydevices/u-boot/blob/boundary-v2020.10/board/boundary/common/
They rely on a couple of new config flags, which I pulled from the result of $ make nitrogen8m_som_4g_defconfig
(they helpfully seem to be the same flags for 2g and 4g boards though)
This needs testing on the modules that shipped with the reform production run, but I expect it should be fine.