marvell: pxa168_eth: fix call balance of pep->clk handling routines

marvell: pxa168_eth: fix call balance of pep->clk handling routines

If the clock pep->clk was not enabled in pxa168_eth_probe,
it should not be disabled in any path.

Conversely, if it was enabled in pxa168_eth_probe, it must be disabled
in all error paths to ensure proper cleanup.

Use the devm_clk_get_enabled helper function to ensure proper call balance
for pep->clk.

Found by Linux Verification Center (linuxtesting.org) with Klever.

Fixes: a49f37eed22b ("net: add Fast Ethernet driver for PXA168.")
Signed-off-by: Vitalii Mordan <mordan@ispras.ru>
Link: https://patch.msgid.link/20241121200658.2203871-1-mordan@ispras.ru
Signed-off-by: Paolo Abeni <pabeni@redhat.com>