Support system flash specific core dump Maxuse size.

[ojayanth]

Currently systems-core dump uses default maxuse side, 10 % of flash size. This need to be update based on machine config.

Systemd-core dump documentation related to this

MaxUse=, KeepFree=
Enforce limits on the disk space taken up by externally stored core dumps. MaxUse= makes sure that old core dumps are removed as soon as the total disk space taken up by core dumps grows beyond this limit (defaults to 10% of the total disk size). KeepFree= controls how much disk space to keep free at least (defaults to 15% of the total disk size). Note that the disk space used by core dumps might temporarily exceed these limits while core dumps are processed. Note that old core dumps are also removed based on time via systemd-tmpfiles(8). Set either value to 0 to turn off size-based clean-up.

[ojayanth]

@geissonator