env: Rename getenv_hex(), getenv_yesno(), getenv_ulong()

We are now using an env_ prefix for environment functions. Rename these
for consistency. Also add function comments in common.h.

Suggested-by: Wolfgang Denk <wd@denx.de>
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/board/gdsys/p1022/controlcenterd-id.c b/board/gdsys/p1022/controlcenterd-id.c
index 61c030a..1813a58 100644
--- a/board/gdsys/p1022/controlcenterd-id.c
+++ b/board/gdsys/p1022/controlcenterd-id.c
@@ -217,7 +217,7 @@
 {
 	ulong addr;
 #ifdef CCDM_SECOND_STAGE
-	addr = getenv_ulong("loadaddr", 16, CONFIG_LOADADDR);
+	addr = env_get_ulong("loadaddr", 16, CONFIG_LOADADDR);
 #else
 	addr = target_addr;
 #endif
@@ -235,7 +235,7 @@
 {
 	ulong addr;
 	/* TODO use other area? */
-	addr = getenv_ulong("loadaddr", 16, CONFIG_LOADADDR);
+	addr = env_get_ulong("loadaddr", 16, CONFIG_LOADADDR);
 	return (u8 *)(addr);
 }
 #endif