MIPS: Loongson1B: Some fixes/updates for LS1B

MIPS: Loongson1B: Some fixes/updates for LS1B

- Fix hanging ethernet issue of LS1B v2.0 by adding pbl field in plat data.
   (It seems that the MAC controller of LS1B v2.0 can only accept pbl=1)
 - Add GMAC1 support and setup MUX in terms of PHY mode.
 - Add CPUFreq support.
 - Add MUX Register Definitions.
 - Add PWM Register Definitions.
 - Update clock register bitfields according to the latest spec.
 - Update clock related stuff.

Signed-off-by: Kelvin Cheung <keguang.zhang@gmail.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/8024/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>