kbuild: rename LDFLAGS to KBUILD_LDFLAGS

Commit a0f97e06a4 ("kbuild: enable 'make CFLAGS=...' to add
additional options to CC") renamed CFLAGS to KBUILD_CFLAGS.

Commit 222d394d30 ("kbuild: enable 'make AFLAGS=...' to add
additional options to AS") renamed AFLAGS to KBUILD_AFLAGS.

Commit 06c5040cdb ("kbuild: enable 'make CPPFLAGS=...' to add
additional options to CPP") renamed CPPFLAGS to KBUILD_CPPFLAGS.

For some reason, LDFLAGS was not renamed.

Using a well-known variable like LDFLAGS may result in accidental
override of the variable.

Kbuild generally uses KBUILD_ prefixed variables for the internally
appended options, so here is one more conversion to sanitize the
naming convention.

I did not touch Makefiles under tools/ since the tools build system
is a different world.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Palmer Dabbelt <palmer@sifive.com>

arch/h8300/Makefile

@@ -20,7 +20,7 @@ KBUILD_CFLAGS += -mint32 -fno-builtin
 KBUILD_CFLAGS += -D__linux__
 KBUILD_CFLAGS += -DUTS_SYSNAME=\"uClinux\"
 KBUILD_AFLAGS += $(aflags-y)
-LDFLAGS += $(ldflags-y)
+KBUILD_LDFLAGS += $(ldflags-y)
 
 ifeq ($(CROSS_COMPILE),)
 CROSS_COMPILE := h8300-unknown-linux-