[SCSI] hpsa: change confusing message to be more clear

The following warning message may be confusing to some users:

dev_warn(&pdev->dev, "Controller claims that "
		"'Bit 2 doorbell reset' is "
		"supported, but not 'bit 5 doorbell reset'.  "
		"Firmware update is recommended.\n");

Most users don't know or care what bit we may be hitting. Also change
"recommended" to "required."

Signed-off-by: Mike Miller <mike.miller@hp.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>