clk: ppc-corenet: rename driver to clk-qoriq

Freescale introduced new ARM-based socs which using the compatible
clock IP block with PowerPC-based socs'. So this driver can be used
on both platforms.
Updated relevant descriptions and renamed this driver to better
represent its meaning and keep the function of driver untouched.

Signed-off-by: Tang Yuantian <Yuantian.Tang@freescale.com>
Signed-off-by: Michael Turquette <mturquette@linaro.org>