The UMS512 Socs have 8 cores contains 6 a55 and 2 a75.
modify the cpu nodes to correct information.

Fixes: 2b488183 ("arm64: dts: sprd: Add support for Unisoc's UMS512")
Cc: stable@vger.kernel.org
Signed-off-by: Cixi Geng <cixi.geng1@unisoc.com>
Link: https://lore.kernel.org/r/20230711162346.5978-1-cixi.geng@linux.devSigned-off-by: Chunyan Zhang <chunyan.zhang@unisoc.com>