isp(4): Rework firmware handling/loading

Correctly identify the active firmware in flash on adapters with
primary and secondary firmware region in flash.
Correctly identify the active NVRAM on adapters with primary
and secondary NVRAM region in flash.

Loading ispfw(4) moved from isp_pci_attach() to isp_reset().
Drop the reference to ispfw(4) after using it so one can kldunload(8) it.
New isp_load_ram() function to load either ispfw(4) or flash firmware
into RISC's RAM.
New functions to read data from flash. The old ones will be removed later.
A bunch of new helper functions to identify and validate active flash
regions for firmware, auxiliary and NVRAM.
Overhaul ISP_FW_* macros and make use of it when comparing firmware
versions. We can handle firmware versions up to 255.255.255.

Firmware load priority slightly changed:
For 27xx and newer adapters:

• load ispfw(4) firmware
• request (active) flash firmware information
• compare version numbers of ispfw(4) and flash firmware
• load firmware with highest version into RISC's RAM
• if loading ispfw(4) is disabled or failed - load firmware from flash
• if everything else fails use MBOX_LOAD_FLASH_FIRMWARE as fallback

For 26xx and older adapters nothing changed:

• load ispfw(4) firmware and load it into RISC's RAM
• if loading ispfw(4) is disabled or failed use MBOX_EXEC_FIRMWARE
• for 26xx a preceding MBOX_LOAD_FLASH_FIRMWARE is used

New read only sysctl(8)'s:
dev.isp.N.fw_version_run: the firmware version actually running
dev.isp.N.fw_version_ispfw: the firmware version provided by ispfw(4)
dev.isp.N.fw_version_flash: the (active) firmware version in flash

While here:

• firmware attribute handling/parsing reworked + renamed defines from ISP2400_FW_ATTR_* to ISP_FW_ATTR_* + changed values to match new handling/parsing + added some more attributes
• enable FLT support on 26xx based adapters
• log level adjustments
• new function return status codes (some for now, some for later use)
• some minor style changes

Tested and approved to work on real hardware with:

• Qlogic ISP 2532 (QLogic QLE2560 8Gb FC Adapter)
• Qlogic ISP 2031 (QLogic QLE2662 16Gbit 2Port FC Adapter)
• Qlogic ISP 2722 (QLogic QLE2690 16Gb FC Adapter)
• Qlogic ISP 2812 (QLogic QLE2772 32Gbit 2Port FC Adapter)

PR: 273263
Reviewed by: mav
Pull Request: https://github.com/freebsd/freebsd-src/pull/877
MFC after: 1 month
Sponsored by: Technical University of Munich

(cherry picked from commit 10ed63fc06cb9902cc783ce8d0086c9aa97ed1e1)