drivers: mrvl_swup: Add debug flag for SMC calls

commit a0222e6220c86bc5ccfb7b66234381541d10d9b8 from
git@git.assembla.com:cavium/WindRiver.linux.git

Introduce debug flag to enable additional timing stats logging.

Change-Id: I2bb255e6512ee45d9770ce5924ea5660df6e9275
Signed-off-by: Sebastien Dubois <sebastien.dubois@nokia.com>
Reviewed-on: https://sj1git1.cavium.com/c/IP/SW/kernel/linux/+/106698


Tested-by: sa_ip-sw-jenkins <sa_ip-sw-jenkins@marvell.com>
Reviewed-by: Sunil Kovvuri Goutham <sgoutham@marvell.com>
Signed-off-by: Li Wang <li.wang@windriver.com>