Booting tip-of-tree on msm8939 we find the following error caused by our
modelling of snoc and snoc_mm as peer devices with the same address space.

[    1.212340] qnoc-msm8939 580000.interconnect_mm: can't request region for resource [mem 0x00580000-0x0059407f]
[    1.212391] qnoc-msm8939 580000.interconnect_mm: Cannot ioremap interconnect bus resource
[    1.221524] qnoc-msm8939: probe of 580000.interconnect_mm failed with error -16

Declaring snoc_mm as a child device of snoc mitigates the fault and is
consistent with a similar extant implementation in qcm2290.
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Link: https://lore.kernel.org/r/20220129032735.2410936-3-bryan.odonoghue@linaro.orgSigned-off-by: Georgi Djakov <djakov@kernel.org>