EDAC/synopsys: Read the error count from the correct register

Currently, the error count is read wrongly from the status register. Read
the count from the proper error count register (ERRCNT).

  [ bp: Massage. ]

Fixes: b500b4a0

 ("EDAC, synopsys: Add ECC support for ZynqMP DDR controller")
Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Michal Simek <michal.simek@xilinx.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20220414102813.4468-1-shubhrajyoti.datta@xilinx.com