rtc: jz4740: fix loading of rtc driver

The current timeout for waiting for WRDY is not always sufficient. Always
increase it to 10000 even on JZ4740. This is technically only required on
JZ4780, where the current symptoms seen after a hard reboot are:

  jz4740-rtc 10003000.rtc: rtc core: registered 10003000.rtc as rtc0
  jz4740-rtc 10003000.rtc: Could not write to RTC registers
  jz4740-rtc: probe of 10003000.rtc failed with error -5

Suggested-by: Alex Smith <alex.smith@imgtec.com>
Cc: Zubair Lutfullah Kakakhel <Zubair.Kakakhel@imgtec.com>
Signed-off-by: Mathieu Malaterre <malat@debian.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>