rpmsg: Add snapshot of RPMSG glink driver for spss

This snapshot is taken as of msm-4.19 'commit <54ada83affde>
("Merge "leds: qpnp-flash-v2: Add support for bharger flash"")'.

This change brings the rpmsg glink driver for spss to Lahaina.
In addition, updates copyright.

Also, fixes error with assigning to iomem structures.

Change-Id: I23da7db2f4729abef02e70cbf8c9fbe7ce4fb8c1
Signed-off-by: Jay Jayanna <jayanna@codeaurora.org>