pie: fix kernel-doc notation warning

Spell a struct member's name correctly to prevent a kernel-doc
warning.

pie.h:38: warning: Function parameter or member 'tupdate' not described in 'pie_params'

Fixes: b42a3d7 ("pie: improve comments and commenting style")
Signed-off-by: Randy Dunlap <[email protected]>
Cc: Leslie Monis <[email protected]>
Cc: "Mohit P. Tahiliani" <[email protected]>
Cc: Gautam Ramakrishnan <[email protected]>
Cc: Jamal Hadi Salim <[email protected]>
Cc: Cong Wang <[email protected]>
Cc: Jiri Pirko <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: rddunlap

include/net/pie.h

@@ -17,7 +17,7 @@
 /**
  * struct pie_params - contains pie parameters
  * @target:		target delay in pschedtime
- * @tudpate:		interval at which drop probability is calculated
+ * @tupdate:		interval at which drop probability is calculated
  * @limit:		total number of packets that can be in the queue
  * @alpha:		parameter to control drop probability
  * @beta:		parameter to control drop probability