sunxi: dram: Use divisor P=1 for PLL5

This configures the PLL5P clock frequency to something in the ballpark
of 1GHz and allows more choices for MBUS and G2D clock frequency
selection (using their own divisors). In particular, it enables the use
of 2/3 clock speed ratio between MBUS and DRAM.

Signed-off-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>