[SCSI] areca: improve driver stability and compatibility

[SCSI] areca: improve driver stability and compatibility

Description:

    1. Implement PCI-Express error recovery function and AER
       capability, especially thanks to Yanmin Zhang's openhanded help
       about AER

    2. Implement the selection of ARCMSR_MAX_XFER_SECTORS_B=4096 if
       firmware version is latter than 1.42

    3. Add arcmsr_done4_abort_postqueue in arcmsr_iop_reset function
       to improve the stability as hot-unplug/plug

    4. Modify the ISR, arcmsr_interrupt routine, to prevent the
       inconsistency with sg_mod driver if application directly calls
       the arcmsr driver w/o passing through scsi midlayer

Signed-off-by: Nick Cheng <nick.cheng@areca.com.tw>
[jejb: unused variable removal]
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>