meta-arm-bsp:trusted-firmware-a: Remove custom do_clean task

The custom do_clean task is not necessary and is misbehaving by not
removing the output files from other tasks.

Change-Id: I5ff837dece88030f24a0dd20c75a738b7b277d61
Issue-Id: SCM-888
Signed-off-by: Diego Sueiro <diego.sueiro@arm.com>
Reviewed-By: Bertrand Marquis <bertrand.marquis@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>

meta-arm/recipes-bsp/trusted-firmware-a/trusted-firmware-a.inc

@@ -82,11 +82,6 @@ DEPENDS += " ${@bb.utils.contains('TFA_UBOOT', '1', 'u-boot', '', d)}"
 do_compile[depends] += " ${@bb.utils.contains('TFA_UBOOT', '1', 'u-boot:do_deploy', '', d)}"
 EXTRA_OEMAKE += "${@bb.utils.contains('TFA_UBOOT', '1', ' BL33=${DEPLOY_DIR_IMAGE}/u-boot.bin', '',d)}"
 
-do_clean() {
-    if [ -f ${S}/Makefile ]; then
-        oe_runmake -C ${S} distclean
-    fi
-}
 
 do_compile() {
     oe_runmake ${TFA_BUILD_TARGET}