rtc: pcf8523: Auto-detect the proper capacitance

Instead of forcing the capacitance to high for all hardware, or
adding another setting to device-tree we auto-detect the proper
capacitance for the oscillator.  First we check the oscillator
for stability based on its power on state, if that fails
switch to the other capacitance and check for stability. The
oscillator can take up to 2 seconds to stabilize.

Signed-off-by: Jon Nettleton <jon.nettleton@gmail.com>
rtc: pcf8523: Warn on possible oscillator problems

Be nice to the operator and let them know of possible reasons
that the rtc device may not be working properly.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Jon Nettleton <jon.nettleton@gmail.com>
rtc: pcf8523: Simplify the oscillator check and enable code

This code was doing way more than it needed to.  Simplify it
so it is easier to understand.