feat(nxp-drivers): add Linflex flush callback

Implement a flush callback for the Linflex UART driver to avoid cases
where the BL31 stage reinitializes the console while there is ongoing TX
initiated by the BL2.

Change-Id: Ic49852f809198362de1f993474c7c45f1439dc98
Signed-off-by: Ghennadi Procopciuc <ghennadi.procopciuc@nxp.com>
2 files changed