microblaze: Add support for distro boot

Add distro boot support for microblaze and enable jtag, qspi,
dhcp, pxe boot targets for distro boot.
Enable DISTRO_DEFAULTS config in microblaze defconfig and also
enable support for spi xilinx driver & spi vendors to access
spi flash by distro boot.

Signed-off-by: T Karthik Reddy <t.karthik.reddy@xilinx.com>
Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
2 files changed