dt-bindings: clock: at91: add sama7g5 pll defines

Add SAMA7G5 specific PLL defines to be referenced in a phandle as a
PMC_TYPE_CORE clock.

Suggested-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
[claudiu.beznea@microchip.com: adapt comit message, adapt sama7g5.c]
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/1605800597-16720-3-git-send-email-claudiu.beznea@microchip.com


Signed-off-by: Stephen Boyd <sboyd@kernel.org>