greybus: Revert "greybus: uart: don't use spin_lock_irq()"

greybus: Revert "greybus: uart: don't use spin_lock_irq()"

This reverts commit bd3c4aa99dc23449699432e0744bcb5af7afa98c.

Someone decided that all use of spin_lock_irq was to be considered a bug
and went on a search-and-replace type "bug-fixing" spree last week.

This is however just plain wrong. Using spin_lock_irq is perfectly fine
in paths were interrupts have not been disabled, and this is in fact
even preferred over the lazy approach of always using spin_lock_irqsave
instead of understanding the code that is being written or modified.

All current uses of spin_lock_irq have already been vetted in this
respect. Also note that it is only used in functions that may sleep,
that is, in functions that must not be called with interrupts disabled
in the first place.

Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>