clk: meson: Rename meson8b-clkc.c to reflect gxbb naming convention

Signed-off-by: Alexander Müller <serveralex@gmail.com>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>
Link: lkml.kernel.org/r/1472319654-59048-2-git-send-email-serveralex@gmail.com