spi: pxa2xx: update outdated reference to pump_transfers()

spi: pxa2xx: update outdated reference to pump_transfers()

The function pump_transfers() was split into
pxa2xx_spi_transfer_one(), pxa2xx_spi_handle_err() and
pxa2xx_spi_set_cs() in commit d5898e19c0d7 ("spi: pxa2xx: Use
core message processing loop").  The comment in
pxa2xx_spi_dma_transfer_complete() still warns about concurrent
calls to pump_transfers(), but the actual operation protected by
dma_running is now spi_finalize_current_transfer().  Update the
reference.

Assisted-by: unnamed:deepseek-v3.2 coccinelle
Signed-off-by: Kexin Sun <kexinsun@smail.nju.edu.cn>
Link: https://patch.msgid.link/20260321105945.8224-1-kexinsun@smail.nju.edu.cn
Signed-off-by: Mark Brown <broonie@kernel.org>