pwm: Drop unused forward declaration from pwm.h

The declaration was necessary until commit cc2d224 ("pwm: Drop
per-chip dbg_show callback").

Signed-off-by: Uwe Kleine-König <[email protected]>
Signed-off-by: Thierry Reding <[email protected]>

Author: Uwe Kleine-König

include/linux/pwm.h

@@ -6,8 +6,6 @@
 #include <linux/mutex.h>
 #include <linux/of.h>
 
-struct seq_file;
-
 struct pwm_chip;
 
 /**