octeontx2-af: Fix irq free in rvu teardown

Current devlink code try to free already freed irqs as the
irq_allocate flag is not cleared after free leading to kernel
crash while removing rvu driver. The patch fixes the irq free
sequence and clears the irq_allocate flag on free.

Fixes: 7304ac45

 ("octeontx2-af: Add mailbox IRQ and msg handlers")
Signed-off-by: Geetha sowjanya <gakula@marvell.com>
Signed-off-by: Hariprasad Kelam <hkelam@marvell.com>
Signed-off-by: Sunil Kovvuri Goutham <sgoutham@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>