docs(imx8m): update build support for imx8mq

Due to the small OCRAM space used for TF-A, we will
meet imx8mq build failure caused by too small RAM size.
We CANNOT support it in TF-A CI. It does NOT mean that
imx8mq will be dropped by NXP. NXP will still actively
maintain it in NXP official release.

Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Change-Id: Iad726ffbc4eedc5f6770612bb9750986b9324ae9
1 file changed