kboot: Centralize ldscript addition

Make the pattern for ldscripts always be
arch/$MACHINE_ARCH/$MACHINE_ARCH.ldscript so we can add it from a
central Makefile. This also moves from ldscript.arch to arch.ldscript to
match the loader's new convention.

Sponsored by:		Netflix
Reviewed by:		tsoome, kevans
Differential Revision:	https://reviews.freebsd.org/D44057

stand/kboot/kboot/Makefile

@@ -51,6 +51,9 @@ HELP_FILENAME=	loader.help.kboot
 .PATH:	${.CURDIR}/arch/${MACHINE_ARCH}
 .include "${.CURDIR}/arch/${MACHINE_ARCH}/Makefile.inc"
 
+# Bring in our ldscript
+LDFLAGS=	-nostdlib -static -T ${.CURDIR}/arch/${MACHINE_ARCH}/${MACHINE_ARCH}.ldscript
+
 # Always add MI sources
 .include	"${BOOTSRC}/loader.mk"
 CFLAGS+=	-I${.CURDIR} -I${.CURDIR}/arch/${MACHINE_ARCH}

stand/kboot/kboot/arch/aarch64/Makefile.inc

@@ -8,5 +8,3 @@ CFLAGS+=	-I${SYSDIR}/contrib/dev/acpica/include
 # load address. set in linker script
 RELOC?=		0x0
 CFLAGS+=	-DRELOC=${RELOC}
-
-LDFLAGS=	-nostdlib -static -T ${.CURDIR}/arch/${MACHINE_ARCH}/ldscript.${MACHINE_ARCH}

stand/kboot/kboot/arch/amd64/Makefile.inc

@@ -1,5 +1,3 @@
 SRCS+=		amd64_tramp.S elf64_freebsd.c load_addr.c fdt_arch.c
 
 CFLAGS+=	-I${SYSDIR}/contrib/dev/acpica/include
-
-LDFLAGS=	-nostdlib -static -T ${.CURDIR}/arch/${MACHINE_ARCH}/ldscript.amd64

stand/kboot/kboot/arch/powerpc64/Makefile.inc

@@ -2,6 +2,4 @@ CFLAGS+=	-mcpu=powerpc64
 
 SRCS+=		ppc64_elf_freebsd.c kerneltramp.S load_addr.c fdt_arch.c
 
-LDFLAGS=	-nostdlib -static -T ${.CURDIR}/arch/${MACHINE_ARCH}/ldscript.powerpc
-
 MK_PIE=		no