rv: Remove redundant assignment to variable retval

Variable retval is being assigned a value that is never read, it is
being re-assigned a new value in both paths of a following if statement.
Remove the assignment.

Cleans up clang-scan warning:
kernel/trace/rv/rv.c:293:2: warning: Value stored to 'retval' is never read [deadcode.DeadStores]
retval = count;

Link: https://lkml.kernel.org/r/[e-mail]

Cc: Masami Hiramatsu <[e-mail]>
Signed-off-by: Colin Ian King <[e-mail]>
Acked-by: Daniel Bristot de Oliveira <[e-mail]>
Signed-off-by: Steven Rostedt (Google) <[e-mail]>

kernel/trace/rv/rv.c

···
 	if (retval)
 		return retval;
 
-	retval = count;
-
 	mutex_lock(&rv_interface_lock);
 
 	if (val)