riscv: use log functions in fdt_fixup

riscv: use log functions in fdt_fixup

Replace printf() and debug() by log_err() and log_debug().

"No reserved memory region found in source FDT\n" is not an error but a
debug information.

%s/can not/cannot/ - use the more common spelling.

Signed-off-by: Heinrich Schuchardt <[email protected]>
Reviewed-by: Bin Meng <[email protected]>
Reviewed-by: Atish Patra <[email protected]>