arm, am335x: add some missing registers and defines for lcd and epwm support

- add missing register defines in struct cm_perpl
  epwmss0clkctrl
  epwmss2clkctrl
  lcdcclkstctrl
- add missing register defines in struct cm_dpll
  clklcdcpixelclk
- add struct pwmss_regs
- add struct pwmss_ecap_regs
- add LCD Controller base LCD_CNTL_BASE
- add PWM0 controller base PWMSS0_BASE

Signed-off-by: Heiko Schocher <hs@denx.de>
Cc: Tom Rini <trini@ti.com>