efi_loader: Rename and move CMD_BOOTEFI_HELLO_COMPILE

efi_loader: Rename and move CMD_BOOTEFI_HELLO_COMPILE

This is not actually a command so the name is confusing. Use
BOOTEFI_HELLO_COMPILE instead. Put it in the efi_loader directory
with the other such config options.

The link rule (for $(obj)/%_efi.so) in scripts/Makefile.lib handles
pulling in efi_crt0.o and efi_reloc.o so drop the 'extra' rules.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>