Basically mlnx-fw-upgrade.sh is used in two places:
1. https://github.com/Azure/sonic-buildimage/blob/201811/files/scripts/syncd.sh#L109
```bash
/usr/bin/mst start
/usr/bin/mlnx-fw-upgrade.sh
/etc/init.d/sxdkernel start
/sbin/modprobe i2c-dev
```
2. https://github.com/Azure/sonic-buildimage/blob/201811/device/mellanox/x86_64-mlnx_msn2700-r0/platform_reboot#L32
```bash
ParseArguments "$@"
${FW_UPGRADE_SCRIPT} --upgrade --verbose
EXIT_CODE="$?"
```
In first case the `stdout` is redirected to `syslog` directly by `systemd`.
Thus, the `syslog` logger is only required in second case.
#### Why I did it
* To improve ASIC/CPLD FW upgrade logging
* To improve CPLD upgrade time
#### How I did it
* Added `syslog` logger support
* Replaced `_pciconf0` -> `_pci_cr0` to reduce CPLD upgrade time
#### How to verify it
1. mlnx-fw-upgrade.sh --upgrade
Install a new FW by specifying FW path (mlnx-fw-upgrade.sh /path/to/FW)
or use default at '/etc/mlnx/fw-SPC.mfa'
Signed-off-by: Stepan Blyschak <stepanb@mellanox.com>
