s32g:linflex: Fix suspend/resume crash

commit  469149903ab3ca644a944e0f6b203eb0ab2862ab from
https://source.codeaurora.org/external/autobsps32/linux



Commit 4e0f83274d5d ("serial:linflex: Stop any dma transfer during INITM")
introduces a subtle bug which crashes the serial driver's resume path.
In suspend/resume, uart_resume_port() first calls the serial driver's
set_termios() callback, and only then the startup() callback. This makes
it so linflex_set_termios() gets to call dma ops before the dma mappings
are correctly set in linflex_startup().
Prevent resumption of dma ops in linflex_set_termios() if we're
resuming. That code will execute in linflex_startup() anyway.

Signed-off-by: Bogdan Hamciuc <bogdan.hamciuc@nxp.com>
Issue: ALB-6516
Signed-off-by: Meng Li <Meng.Li@windriver.com>