dmaengine: bam_dma: fix return of bam_dma_irq()

While performing suspend/resume, we were getting below kernel crash.

[   54.541672] [FTS][Info]gesture suspend...
[   54.605256] [FTS][Error][GESTURE]Enter into gesture(suspend) failed!
[   54.605256]
[   58.345850] irq event 10: bogus return value fffffff3
......

[   58.345966] [<ffff0000080830f0>] el1_irq+0xb0/0x124
[   58.345971] [<ffff000008085360>] arch_cpu_idle+0x10/0x18
[   58.345975] [<ffff0000081077f4>] do_idle+0x1ac/0x1e0
[   58.345979] [<ffff0000081079c8>] cpu_startup_entry+0x20/0x28
[   58.345983] [<ffff000008a80ed0>] rest_init+0xd0/0xdc
[   58.345988] [<ffff0000091c0b48>] start_kernel+0x390/0x3a4
[   58.345990] handlers:
[   58.345994] [<ffff0000085120d0>] bam_dma_irq

The reason for the crash we found is, bam_dma_irq() was returning
negative value when the device resumes in some conditions.

In addition, the irq handler should have one of the below return values.

IRQ_NONE            interrupt was not from this device or was not handled
IRQ_HANDLED         interrupt was handled by this device
IRQ_WAKE_THREAD     handler requests to wake the handler thread

Therefore, to resolve this crash, we have changed the return value to
IRQ_NONE.

Signed-off-by: Parth Y Shah <sparth1292@gmail.com>
Link: https://lore.kernel.org/r/1607322820-7450-1-git-send-email-sparth1292@gmail.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>