microblaze: Do not place u-boot to reserved memory location

Microblaze can also have reserved space in DT which u-boot has to avoid to
placing self to that location. The same change was done in Zynqmp by commit
ce39ee28 ("zynqmp: Do not place u-boot to reserved memory location").

This feature was tested with this memory description on kc705:

	memory {
		device_type = "memory";
		reg = <0x80000000 0x40000000>;
	};

	reserved-memory {
		#address-cells = <1>;
		#size-cells = <1>;
		ranges;

		alloc@b00000000 {
			reg = <0xb0000000 0x10000000>;
			no-map;
		};

		alloc@a8000000 {
			reg = <0xa8000000 0x00010000>;
			no-map;
		};
	};

And in U-Boot log you can check u-boot relocation address and reserved
locations.
U-Boot 2022.01-03974-gb1b4c2dea9b9 (Feb 25 2022 - 11:59:48 +0100)

Model: Xilinx MicroBlaze
DRAM:  1 GiB
Flash: 128 MiB
Loading Environment from nowhere... OK
In:    serial
Out:   serial
Err:   serial
Model: Xilinx MicroBlaze
Net:   AXI EMAC: 40c00000, phyaddr 7, interface gmii
eth0: ethernet@40c00000
U-BOOT for microblaze-generic

U-Boot-mONStR> bdi
...
DRAM bank   = 0x00000000
-> start    = 0x80000000
-> size     = 0x40000000
...
relocaddr   = 0xaff69000
...
lmb_dump_all:
 memory.cnt  = 0x1
 memory[0]	[0x80000000-0xbfffffff], 0x40000000 bytes flags: 0
 reserved.cnt  = 0x3
 reserved[0]	[0xa8000000-0xa800ffff], 0x00010000 bytes flags: 4
 reserved[1]	[0xafe87bb0-0xafffffff], 0x00178450 bytes flags: 0
 reserved[2]	[0xb0000000-0xbfffffff], 0x10000000 bytes flags: 4

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Link: https://lore.kernel.org/r/ea0a8ccce723478eb518f6fdceb91d4f129efb68.1646122398.git.michal.simek@xilinx.com