treewide: Remove CONFIG_SYS_UBOOT_START from configs board files
As previous CONFIG_SYS_UBOOT_START is now set by default to
CONFIG_SYS_TEXT_BASE when not defined, CONFIG_SYS_UBOOT_START
can be removed from include/configs board files.
Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Acked-by: Lukasz Majewski <lukma@denx.de>