env: Move env_set() out of cmd/nvedit.c and in to env/common.c

Inside of env/common.c we already have our helper env_set_xxx functions,
and even have a comment that explains why env_set() itself wasn't moved.
We now handle that move. This requires that we rename the previous
_do_env_set() to env_do_env_set() and note it as an internal env
function. Add comments about this function to explain why we do this
when we add the prototype. Add a new function, env_inc_id() to allow for
the counter to be updated by both commands and callers, and document
this as well by the prototype.

Signed-off-by: Tom Rini <trini@konsulko.com>

cmd/Makefile

@@ -128,6 +128,7 @@ endif
 obj-$(CONFIG_CMD_MUX) += mux.o
 obj-$(CONFIG_CMD_NAND) += nand.o
 obj-$(CONFIG_CMD_NET) += net.o
+obj-$(CONFIG_ENV_SUPPORT) += nvedit.o
 obj-$(CONFIG_CMD_NVEDIT_EFI) += nvedit_efi.o
 obj-$(CONFIG_CMD_ONENAND) += onenand.o
 obj-$(CONFIG_CMD_OSD) += osd.o
@@ -245,9 +246,6 @@ endif # !CONFIG_SPL_BUILD
 
 obj-$(CONFIG_$(SPL_)CMD_TLV_EEPROM) += tlv_eeprom.o
 
-# core command
-obj-y += nvedit.o
-
 obj-$(CONFIG_CMD_BCM_EXT_UTILS) += broadcom/
 
 filechk_data_gz = (echo "static const char data_gz[] ="; cat $< | scripts/bin2c; echo ";")