imx: imx8qm/qxp: Fix issue in get_effective_memsize

imx: imx8qm/qxp: Fix issue in get_effective_memsize

When Trusty OS allocates the mem region from 0xfe0000000-0xffffffff,
the get_effective_memsize does not return correct memory size.
There is a check in get_effective_memsize to find the memreg where
the u-boot is running, and return the size of that memreg as the result
of get_effective_memsize. When using aligned start, the value is
0x80200000 since it is 2MB aligned. Thus the finding of memreg will
fail and return the PHYS_SDRAM_1_SIZE because u-boot text base is
0x80020000. This cause u-boot is relocated to the high memory where has
been occupied by Trusty OS.

Reviewed-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Ye Li <ye.li@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>