lib: os: spsc_pbuf: Improve data cache configuration

Use CONFIG_DCACHE_LINE_SIZE to determine distance between
fields modified by different cores.
Add option which specifies what is the data cache line
of the remote core. Maximum from local and remote cache
line sizes is used as distance and alignement.

Signed-off-by: Krzysztof Chruscinski <krzysztof.chruscinski@nordicsemi.no>