Previously "reading" clock info (and part info) also, as a side
effect, wrote the flash timing register. Instead, be more safe:
"reading" should only read. Write paths still refresh timing,
coping with changes the application code may have made.
Also rename the routine which sets flash timing, indicating what
it's really doing; it's got nothing to do with a "mode".
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>