remoteproc: do cache invalidation before reading rsc_table status

[iuliana-prodan]

Do a cache invalidation before reading the resource table's status since this ca be in a cacheable region.

[iuliana-prodan]

cc @carlocaione @arnopo

[iuliana-prodan]

Changes since v1:

• make cache invalidation optional based on VIRTIO_CACHED_RSC_TABLE;
• add VIRTIO_CACHED_RSC_TABLE as option.

[iuliana-prodan]

Changes since v2:

• use defines, added in header, for cache flush/invalidate functions.

LE: the checkpatch issue is a false-positive.

[arnopo]

Please also update https://github.com/OpenAMP/open-amp/blob/main/README.md

[iuliana-prodan]

Changes since v3:

• fix checkpatch warning;
• update README in new commit.

[iuliana-prodan]

Changes since v4:

• in order to fix checkpatch warnings I've added 2 arguments for RSC_TABLE_FLUSH and RSC_TABLE_INVALIDATE,

[iuliana-prodan]

Changes since v5:

• call RSC_TABLE_INVALIDATE with sizeof(struct..);
• do not use address of the pointer for metal_cache_flush/metal_cache_invalidate;

[iuliana-prodan]

Changes since v6:

• do flush/invalidate also for write/read config;

[iuliana-prodan]

Changes since v7: keep the newlines consistent among all the RSCTABLE* calls;