i3c: master: dw: remove dead code from dw_i3c_master_*_xfers()

Detected by CoverityScan (Event result_independent_of_operands):
"(i3c_xfers + i).len > 65536" is always false regardless of the values
of its operands. This occurs as the logical operand of "if"

"(i2c_xfers + i).len > 65536" is always false regardless of the values
of its operands. This occurs as the logical operand of "if"

Signed-off-by: Vitor Soares <vitor.soares@synopsys.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>