boot/arm-trusted-firmware: don't pass TARGET_CONFIGURE_OPTS when building

boot/arm-trusted-firmware: don't pass TARGET_CONFIGURE_OPTS when building

Passing CFLAGS/CPPFLAGS in the environment confuses the ATF version
provided by Marvell, and we in fact only need to pass CROSS_COMPILE,
which is already in ARM_TRUSTED_FIRMWARE_MAKE_OPTS.

We however keep TARGET_MAKE_ENV so that the PATH with $(HOST_DIR) is
kept.

This change has been tested with all current defconfigs that build
ATF:

 - arm_juno
 - bananapi_m64
 - freescale_imx8mqevk
 - friendlyarm_nanopi_a64
 - friendlyarm_nanopi_neo2
 - nitrogen8m
 - olimex_a64_olinuxino
 - orangepi_pc2
 - orangepi_prime
 - orangepi_win
 - orangepi_zero_plus2
 - pine64
 - pine64_sopine
 - solidrun_macchiatobin_mainline
 - solidrun_macchiatobin_marvell
 - zynqmp_zcu106

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>