drm/i915/fbc: fix the FBC kernel-doc warnings

Fix the recently introduced 'make htmldocs' warnings:

$ make htmldocs 2>&1 > /dev/null | grep i915
./drivers/gpu/drm/i915/display/intel_fbc.c:635: warning: Excess function parameter 'i915' description in 'intel_fbc_is_active'
./drivers/gpu/drm/i915/display/intel_fbc.c:1638: warning: Excess function parameter 'i915' description in 'intel_fbc_handle_fifo_underrun_irq'
./drivers/gpu/drm/i915/display/intel_fbc.c:635: warning: Function parameter or member 'fbc' not described in 'intel_fbc_is_active'
./drivers/gpu/drm/i915/display/intel_fbc.c:635: warning: Excess function parameter 'i915' description in 'intel_fbc_is_active'
./drivers/gpu/drm/i915/display/intel_fbc.c:1638: warning: Function parameter or member 'fbc' not described in 'intel_fbc_handle_fifo_underrun_irq'
./drivers/gpu/drm/i915/display/intel_fbc.c:1638: warning: Excess function parameter 'i915' description in 'intel_fbc_handle_fifo_underrun_irq'

Fixes: e49a656b ("drm/i915/fbc: Start passing around intel_fbc")
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211115140549.27629-1-jani.nikula@intel.com

drivers/gpu/drm/i915/display/intel_fbc.c

@@ -624,7 +624,7 @@ int intel_fbc_set_false_color(struct intel_fbc *fbc, bool enable)
 
 /**
  * intel_fbc_is_active - Is FBC active?
- * @i915: i915 device instance
+ * @fbc: The FBC instance
  *
  * This function is used to verify the current state of FBC.
  *
@@ -1592,7 +1592,7 @@ static void intel_fbc_underrun_work_fn(struct work_struct *work)
 
 /*
  * intel_fbc_reset_underrun - reset FBC fifo underrun status.
- * @i915: i915 device instance
+ * @fbc: The FBC instance
  *
  * See intel_fbc_handle_fifo_underrun_irq(). For automated testing we
  * want to re-enable FBC after an underrun to increase test coverage.
@@ -1622,7 +1622,7 @@ int intel_fbc_reset_underrun(struct intel_fbc *fbc)
 
 /**
  * intel_fbc_handle_fifo_underrun_irq - disable FBC when we get a FIFO underrun
- * @i915: i915 device instance
+ * @fbc: The FBC instance
  *
  * Without FBC, most underruns are harmless and don't really cause too many
  * problems, except for an annoying message on dmesg. With FBC, underruns can