meson: Rename platform directory to amlogic

Meson is the internal code name for the SoC family. The correct name for
the platform should be Amlogic. Change the name of the platform
directory.

Signed-off-by: Carlo Caione <ccaione@baylibre.com>
Change-Id: Icc140e1ea137f12117acbf64c7dcb1a8b66b345d
38 files changed