dt-bindings: clock: gcc-msm8917: Add definition for GPLL0_SLEEP_CLK_SRC

Add the missing #define for GPLL0_SLEEP_CLK_SRC, the parent clock of
GPLL0_EARLY.

Signed-off-by: Otto Pflüger <otto.pflueger@abscue.de>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230802170317.205112-2-otto.pflueger@abscue.de


Signed-off-by: Bjorn Andersson <andersson@kernel.org>