Makefile: Change default target to all

According to README.gnuefi,

To build the sample EFI applications provided in subdirectory "apps",
simply invoke "make" in the toplevel directory (the directory
containing this README file).  This should build lib/libefi.a and
gnuefi/libgnuefi.a first and then all the EFI applications such as a
apps/t6.efi.

The default target of top directory Makefile should be all instead of
gnuefi.

Signed-off-by: Letu Ren <fantasquex@gmail.com>

Makefile

@@ -44,10 +44,11 @@ VPATH = $(SRCDIR)
 include $(SRCDIR)/Make.defaults
 
 SUBDIRS = lib gnuefi inc apps
-gnuefi: lib
 
 all:	check_gcc $(SUBDIRS)
 
+gnuefi: lib
+
 mkvars:
 	@echo AR=$(AR)
 	@echo ARCH=$(ARCH)