arm64: dts: qcom: msm8916/39: Move mpss_mem size to boards

arm64: dts: qcom: msm8916/39: Move mpss_mem size to boards

The modem firmware size is typically highly device-specific.
The current size of the mpss_mem region in msm8916.dtsi (0x2b00000)
only works for some APQ8016 devices without full-featured modem,
such as the DragonBoard 410c.

The full modem firmware is typically about twice as large (~45 MiB
-> ~90 MiB) but also varies by a few MiB from device to device. Since
these devices are quite memory-constrained nowadays it's important to
minimize the unnecessary memory reservations.

Make it clear that each board needs to specify the necessary mpss_mem
size by replacing the DB410c-specific size in msm8916.dtsi with a
simple comment. &mpss_mem is disabled by default so it's fine to leave
some properties up to the boards if they want to enable it.

Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Link: https://lore.kernel.org/r/20230911-msm8916-rmem-v1-8-b7089ec3e3a1@gerhold.net
Signed-off-by: Bjorn Andersson <andersson@kernel.org>