DA8xx: kill duplicate #define DA8XX_PLL1_BASE

Commit 044ca015 (davinci: da850/omap-l138: add
support for SoC suspend) introduced DA8XX_PLL1_BASE despite PLL1 exists only on
DA850/OMAP-L138 and da850.c even already #define'd DA850_PLL1_BASE. Kill the
duplicate macro, renaming an existing reference to it...

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>