boot/uboot: Remove obsolete CONFIG_NOSOFTFLOAT flag

boot/uboot: Remove obsolete CONFIG_NOSOFTFLOAT flag

This flag seems to be obsolete. There is no piece of code in the U-Boot source
tree referencing CONFIG_NOSOFTFLOAT.

Unfortunatly the use of this flag is not documented here. Maybe it's about this
old workaround:
http://lists.denx.de/pipermail/u-boot/2007-March/020282.html

However, this patch has been declined:
http://www.denx.de/wiki/view/U-Boot/PatchStatus?rev=1.27

Since no other configure options are used, remove also UBOOT_CONFIGURE_OPTS.

Signed-off-by: Jörg Krause <jkrause@posteo.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>