env: add ENV_ERASE_PTR macro

Add ENV_ERASE_PTR macro to handle erase opts and remove the associated
ifdef.

This patch is a extension of previous commit 82b2f41357 ("env_internal.h:
add alternative ENV_SAVE_PTR macro").

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>

env/ext4.c

@@ -188,6 +188,5 @@ U_BOOT_ENV_LOCATION(ext4) = {
 	ENV_NAME("EXT4")
 	.load		= env_ext4_load,
 	.save		= ENV_SAVE_PTR(env_ext4_save),
-	.erase		= CONFIG_IS_ENABLED(CMD_ERASEENV) ? env_ext4_erase :
-							    NULL,
+	.erase		= ENV_ERASE_PTR(env_ext4_erase),
 };

env/mmc.c

@@ -233,7 +233,6 @@ fini:
 	return ret;
 }
 
-#if defined(CONFIG_CMD_ERASEENV)
 static inline int erase_env(struct mmc *mmc, unsigned long size,
 			    unsigned long offset)
 {
@@ -279,7 +278,6 @@ static int env_mmc_erase(void)
 
 	return ret;
 }
-#endif /* CONFIG_CMD_ERASEENV */
 #endif /* CONFIG_CMD_SAVEENV && !CONFIG_SPL_BUILD */
 
 static inline int read_env(struct mmc *mmc, unsigned long size,
@@ -394,8 +392,6 @@ U_BOOT_ENV_LOCATION(mmc) = {
 	.load		= env_mmc_load,
 #ifndef CONFIG_SPL_BUILD
 	.save		= env_save_ptr(env_mmc_save),
-#if defined(CONFIG_CMD_ERASEENV)
-	.erase		= env_mmc_erase,
-#endif
+	.erase		= ENV_ERASE_PTR(env_mmc_erase)
 #endif
 };

include/env_internal.h

@@ -211,6 +211,7 @@ struct env_driver {
 #endif
 
 #define ENV_SAVE_PTR(x) (CONFIG_IS_ENABLED(SAVEENV) ? (x) : NULL)
+#define ENV_ERASE_PTR(x) (CONFIG_IS_ENABLED(CMD_ERASEENV) ? (x) : NULL)
 
 extern struct hsearch_data env_htab;