env: Move get/set_default_env() to env.h

Move these functions to the new header file and rename set_default_env()
to env_set_default() so that it has a consistent env_ prefix.

Acked-by: Joe Hershberger <joe.hershberger@ni.com>
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/env/sf.c b/env/sf.c
index 4f92ae0..5531293 100644
--- a/env/sf.c
+++ b/env/sf.c
@@ -10,6 +10,7 @@
  */
 #include <common.h>
 #include <dm.h>
+#include <env.h>
 #include <environment.h>
 #include <malloc.h>
 #include <spi.h>
@@ -48,7 +49,7 @@
 				     CONFIG_ENV_SPI_MAX_HZ, CONFIG_ENV_SPI_MODE,
 				     &new);
 	if (ret) {
-		set_default_env("spi_flash_probe_bus_cs() failed", 0);
+		env_set_default("spi_flash_probe_bus_cs() failed", 0);
 		return ret;
 	}
 
@@ -60,7 +61,7 @@
 			CONFIG_ENV_SPI_CS,
 			CONFIG_ENV_SPI_MAX_HZ, CONFIG_ENV_SPI_MODE);
 		if (!env_flash) {
-			set_default_env("spi_flash_probe() failed", 0);
+			env_set_default("spi_flash_probe() failed", 0);
 			return -EIO;
 		}
 	}
@@ -161,7 +162,7 @@
 	tmp_env2 = (env_t *)memalign(ARCH_DMA_MINALIGN,
 			CONFIG_ENV_SIZE);
 	if (!tmp_env1 || !tmp_env2) {
-		set_default_env("malloc() failed", 0);
+		env_set_default("malloc() failed", 0);
 		ret = -EIO;
 		goto out;
 	}
@@ -256,7 +257,7 @@
 
 	buf = (char *)memalign(ARCH_DMA_MINALIGN, CONFIG_ENV_SIZE);
 	if (!buf) {
-		set_default_env("malloc() failed", 0);
+		env_set_default("malloc() failed", 0);
 		return -EIO;
 	}
 
@@ -267,7 +268,7 @@
 	ret = spi_flash_read(env_flash,
 		CONFIG_ENV_OFFSET, CONFIG_ENV_SIZE, buf);
 	if (ret) {
-		set_default_env("spi_flash_read() failed", 0);
+		env_set_default("spi_flash_read() failed", 0);
 		goto err_read;
 	}