i2c: spacemit: fix spurious IRQ handling returning IRQ_HANDLED

i2c: spacemit: fix spurious IRQ handling returning IRQ_HANDLED

When the interrupt status register reads zero, the handler should
return IRQ_NONE instead of IRQ_HANDLED. What the return value
actually feeds into is the spurious interrupt accounting in
note_interrupt(): falsely claiming IRQ_HANDLED defeats the "irq XX:
nobody cared" detection, so a stuck interrupt source would never be
caught.

Fixes: 5ea558473fa3 ("i2c: spacemit: add support for SpacemiT K1 SoC")
Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>
Cc: <stable@vger.kernel.org> # v6.15+
Reviewed-by: Troy Mitchell <troy.mitchell@linux.spacemit.com>
Reviewed-by: Mukesh Savaliya <mukesh.savaliya@oss.qualcomm.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Link: https://lore.kernel.org/r/ef8b623f45d4e430721e46572c2598d882044aed.1783667875.git.xiaopei01@kylinos.cn