clocksource/drivers/stm32: Fix all kernel-doc warnings

Add a "Returns:" section in one function description.
Use the correct function name in another function description.

These changes prevent 2 warnings:

timer-stm32.c:79: warning: No description found for return value of 'stm32_timer_of_bits_get'
timer-stm32.c:189: warning: expecting prototype for stm32_timer_width(). Prototype was for stm32_timer_set_width() instead

Signed-off-by: Randy Dunlap <[e-mail]>
Cc: Daniel Lezcano <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Fabrice Gasnier <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Signed-off-by: Daniel Lezcano <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/clocksource/timer-stm32.c

···
  * Accessor helper to get the number of bits in the timer-of private
  * structure.
  *
- * Returns an integer corresponding to the number of bits.
+ * Returns: an integer corresponding to the number of bits.
  */
 static int stm32_timer_of_bits_get(struct timer_of *to)
 {
···
 }
 
 /**
- * stm32_timer_width - Sort out the timer width (32/16)
+ * stm32_timer_set_width - Sort out the timer width (32/16)
  * @to: a pointer to a timer-of structure
  *
  * Write the 32-bit max value and read/return the result. If the timer