arm64: dts: meson: khadas-vim3: move model to g12b-khadas-vim3 dtsi

The common meson-khadas-vim3.dtsi is now shared with VIM3L so move the
VIM3 model name to meson-g12b-khadas-vim3.dtsi.

meson-sm1-khadas-vim3l.dts contains the VIM3L model name.

changes in v2
- fix typo in commit message

Signed-off-by: Christian Hewitt <christianshewitt@gmail.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://lore.kernel.org/r/1583378508-14312-1-git-send-email-christianshewitt@gmail.com