drm/vkms: Fix all kernel-doc warnings of the vkms_composer file

Fix the following warnings:

drivers/gpu/drm/vkms/vkms_composer.c:42: warning: Function parameter or member 'frame_info' not described in 'pre_mul_alpha_blend'
drivers/gpu/drm/vkms/vkms_composer.c:42: warning: Excess function parameter 'src_frame_info' description in 'pre_mul_alpha_blend'
drivers/gpu/drm/vkms/vkms_composer.c:93: warning: Cannot understand  * @wb_frame_info: The writeback frame buffer metadata
 on line 93 - I thought it was a doc line

by correcting variable names and adding function name.
Signed-off-by: Maíra Canal <mcanal@igalia.com>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Signed-off-by: Maíra Canal <mairacanal@riseup.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20230508220030.434118-2-mcanal@igalia.com

drivers/gpu/drm/vkms/vkms_composer.c

@@ -23,7 +23,7 @@ static u16 pre_mul_blend_channel(u16 src, u16 dst, u16 alpha)
 
 /**
  * pre_mul_alpha_blend - alpha blending equation
- * @src_frame_info: source framebuffer's metadata
+ * @frame_info: Source framebuffer's metadata
  * @stage_buffer: The line with the pixels from src_plane
  * @output_buffer: A line buffer that receives all the blends output
  *
@@ -90,11 +90,13 @@ static void fill_background(const struct pixel_argb_u16 *background_color,
 }
 
 /**
- * @wb_frame_info: The writeback frame buffer metadata
+ * blend - blend the pixels from all planes and compute crc
+ * @wb: The writeback frame buffer metadata
  * @crtc_state: The crtc state
  * @crc32: The crc output of the final frame
  * @output_buffer: A buffer of a row that will receive the result of the blend(s)
  * @stage_buffer: The line with the pixels from plane being blend to the output
+ * @row_size: The size, in bytes, of a single row
  *
  * This function blends the pixels (Using the `pre_mul_alpha_blend`)
  * from all planes, calculates the crc32 of the output from the former step,