net/bnxt: add context list for timers

net/bnxt: add context list for timers

Add context in ULP for timers.
The alarm callback needs to have a valid context pointer when it is
invoked. The context could become invalid if the port goes down and
the callback is invoked before it is cancelled.

Signed-off-by: Kishore Padmanabha <kishore.padmanabha@broadcom.com>
Signed-off-by: Venkat Duvvuru <venkatkumar.duvvuru@broadcom.com>
Reviewed-by: Randy Schacher <stuart.schacher@broadcom.com>
Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>