[SCSI] ipr: increase the dump size for 64 bit adapters

Currently the size of the dump generated by the driver is limited
in 4MB, which is insufficient to gather much useful data from the
new 64 bit adapters.

This patch makes the needed changes to increase the dump limit
for the 64 bit adapters to 32MB, or even to a bigger value in the
future, but keeping the current limitations for the legacy 32 bit
adapters.

Signed-off-by: Kleber Sacilotto de Souza <klebers@linux.vnet.ibm.com>
Acked-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>