serial: omap: Disable PM runtime autoidle to remove pm_runtime_irq_safe()

We want to remove the use of pm_runtime_irq_safe() from serial drivers
to allow making PM runtime handling generic. Let's simplify things by
disabling PM runtime autoidle for omap-serial as this driver has been
deprecated for years because of the 8250_omap driver.

There are still some omap-serial users that seem to hang on to it for
some unknown rs485 reasons it seems. But presumably those folks do not
need PM runtime autoidle with omap-serial, and hopefully can just move
to using 8250_omap driver instead.

For 8250_omap driver, we will eventually move to use generic serial
layer PM based on patches done by Andy Shevchenko to remove
pm_runtime_irq_safe() usage.

Cc: Andy Shevchenko <andriy.shevchenko@intel.com>
Cc: Dario Binacchi <dariobin@libero.it>
Cc: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Link: https://lore.kernel.org/r/20210727103149.51175-1-tony@atomide.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>