drm/fb-helper: Fix typo in parameter description

Fix typo in parameter description.

Fixes: 4be9bd10e22d ("drm/fb_helper: Allow leaking fbdev smem_start")
Signed-off-by: Wei Yongjun <[e-mail]>
Acked-by: Neil Armstrong <[e-mail]>
Signed-off-by: Neil Armstrong <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/drm_fb_helper.c

···
 #if IS_ENABLED(CONFIG_DRM_FBDEV_LEAK_PHYS_SMEM)
 static bool drm_leak_fbdev_smem = false;
 module_param_unsafe(drm_leak_fbdev_smem, bool, 0600);
-MODULE_PARM_DESC(fbdev_emulation,
+MODULE_PARM_DESC(drm_leak_fbdev_smem,
 		 "Allow unsafe leaking fbdev physical smem address [default=false]");
 #endif