i2c: npcm7xx: Use NULL instead of 0 for pointer

i2c: npcm7xx: Use NULL instead of 0 for pointer

Pointers should use NULL instead of explicit '0', as pointed out by
sparse:

  i2c-npcm7xx.c:1387:61: warning: Using plain integer as NULL pointer

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Reviewed-by: Paul Menzel <pmenzel@molgen.mpg.de>
Reviewed-by: Tali Perry <tali.perry1@gmail.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Link: https://lore.kernel.org/r/20260216085825.70568-2-krzysztof.kozlowski@oss.qualcomm.com