board: st: stm32mp1: update load address for FIT examples

Update kernel load address for FIT examples to avoid relocation:
- Kernel example uses Image.gz with U-Boot gzip decompression
  at final kernel location 0x0xC0008000.
- Copro example loads zImage at a correct location (0xC4000000),
  to avoid zImage relocation before decompression by kernel code.

An other solution to avoid zImage relocation is to align
the kernel load and entry address with the real location in FIT
(the relocation of zImage is skipped in U-Boot bootm command for
identical address) but it is less flexible because this offset
depends on FIT content:

For example:

## Loading kernel from FIT Image at c2000000 ...
   Using 'ev1' configuration
   Trying 'kernel' kernel subimage
     Description:  Linux kernel
     Created:      2020-10-22   9:08:32 UTC
     Type:         Kernel Image
     Compression:  uncompressed
     Data Start:   0xc20000cc

The kernel offset in FIT is 0xCC in FIT and zImage is decompressed at
0xC0008000 by kernel code:

kernel {
	description = "Linux kernel";
	data = /incbin/("zImage");
	type = "kernel";
	arch = "arm";
	os = "linux";
	compression = "none";
	load = <0xC20000cc>;
	entry = <0xC20000cc>;
	hash-1 {
		algo = "sha1";
	};
};

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@st.com>