drm/ast: Manage release of firmware backup memory

The ast driver keeps a backup copy of the DP501 encoder's firmware. This
patch adds managed release of the allocated memory.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200730135206.30239-9-tzimmermann@suse.de

drivers/gpu/drm/ast/ast_main.c

@@ -33,6 +33,7 @@
 #include <drm/drm_drv.h>
 #include <drm/drm_gem.h>
 #include <drm/drm_gem_vram_helper.h>
+#include <drm/drm_managed.h>
 
 #include "ast_drv.h"
 
@@ -231,11 +232,11 @@ static int ast_detect_chip(struct drm_device *dev, bool *need_post)
 			ast->tx_chip_type = AST_TX_SIL164;
 			break;
 		case 0x08:
-			ast->dp501_fw_addr = kzalloc(32*1024, GFP_KERNEL);
+			ast->dp501_fw_addr = drmm_kzalloc(dev, 32*1024, GFP_KERNEL);
 			if (ast->dp501_fw_addr) {
 				/* backup firmware */
 				if (ast_backup_fw(dev, ast->dp501_fw_addr, 32*1024)) {
-					kfree(ast->dp501_fw_addr);
+					drmm_kfree(dev, ast->dp501_fw_addr);
 					ast->dp501_fw_addr = NULL;
 				}
 			}
@@ -444,6 +445,4 @@ void ast_device_destroy(struct ast_private *ast)
 {
 	/* enable standard VGA decode */
 	ast_set_index_reg(ast, AST_IO_CRTC_PORT, 0xa1, 0x04);
-
-	kfree(ast->dp501_fw_addr);
 }