test/py: test_efi_fit: Update #size-cells to 1

test/py: test_efi_fit: Update #size-cells to 1

test_efi_fit tests fail on RISC-V currently. This is due to the
RISC-V arch_fixup_fdt() checks the #size-cells of the root node
in order to correctly fix up the reserved memory node.

Per the DT binding, the /reserved-memory node requires both
<#address-cells> and <#size-cells> and they should use the same
values as the root node. For the root node, it's not very useful
if <#size-cells> is zero.

Update #size-cells to 1 so tests can pass.

Signed-off-by: Bin Meng <bin.meng@windriver.com>