counter: 104-quad-8: Fix race getting function mode and direction

The quad8_action_read() function checks the Count function mode and
Count direction without first acquiring a lock. This is a race condition
because the function mode could change by the time the direction is
checked.

Because the quad8_function_read() already acquires a lock internally,
the quad8_function_read() is refactored to spin out the no-lock code to
a new quad8_function_get() function.

To resolve the race condition in quad8_action_read(), a lock is acquired
before calling quad8_function_get() and quad8_direction_read() in order
to get both function mode and direction atomically.

Fixes: f1d8a071d45b ("counter: 104-quad-8: Add Generic Counter interface support")
Cc: [email protected]
Link: https://lore.kernel.org/r/[email protected]/
Signed-off-by: William Breathitt Gray <[email protected]>

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