DA8xx: fix LPSC constants

Some of the LPSC constants were incorrect, and some were missing. This
commit fixes the incorrect constants (which were not used anywhere in
the tree) and adds all constants for both DA830 and DA850, as per the
TI datasheets.

Signed-off-by: Laurence Withers <lwithers@guralp.com>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>