imx-base.inc: Set a default provider for u-boot-mxsboot-native
The O.S. Systems Embedded Linux provides an alternative version of
U-Boot and, for completeness, an alternative recipe for
u-boot-mxsboot-native.
The provider, in imx-base.inc, had no default thus raising a
warning. This turns the u-boot-fslc-mxsboot-native as the default
provider but allows custom distributions to override it.
Change-Id: I46799f9ec744a074d95c383561cf0cbddb26e151 Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
