tfa-layerscape: fix create_pbl and byte_swap host build

tfa-layerscape: fix create_pbl and byte_swap host build

- make create_pbl and byte_swap as host tools

- fix a bug that maybe use the cross compiler
to compile create_pbl and byte_swap:

	# -a option appends the image for Chassis 3 devices in case of non secure boot
	aarch64-openwrt-linux-musl-gcc -Wall -Werror -pedantic -std=c99 -O2
	 -DVERSION=v1.5(release):reboot-10604-ge9216b3336 -D_GNU_SOURCE -D_XOPEN_SOURCE=700
	 -c -o create_pbl.o create_pbl.c
	cc1: note: someone does not honour COPTS correctly, passed 0 times
	  LD      create_pbl
	/usr/bin/ld: create_pbl.o: Relocations in generic ELF (EM: 183)
	/usr/bin/ld: create_pbl.o: Relocations in generic ELF (EM: 183)
	/usr/bin/ld: create_pbl.o: Relocations in generic ELF (EM: 183)
	create_pbl.o: error adding symbols: File in wrong format
	collect2: error: ld returned 1 exit status
	Makefile:43: recipe for target create_pbl failed
	make[4]: *** [create_pbl] Error 1
	plat/nxp/tools/pbl_ch2.mk:45: recipe for target pbl failed
	make[3]: *** [pbl] Error 2

- add tfa- prefix to all tools in order to avoid future clashes with
  other toolnames

Signed-off-by: Biwen Li <biwen.li@nxp.com>
[added missing HOST_CFLAGS, added tfa- prefix to the tools]
Signed-off-by: Petr Štetiar <ynezz@true.cz>