net: stmmac: Fix unbalanced IRQ wake disable warning on single irq case

Commit a23aa040 ("net: stmmac: ethtool: Fixed calltrace caused by
unbalanced disable_irq_wake calls") introduced checks to prevent
unbalanced enable and disable IRQ wake calls. However it only
initialized the auxiliary variable on one of the paths,
stmmac_request_irq_multi_msi(), missing the other,
stmmac_request_irq_single().

Add the same initialization on stmmac_request_irq_single() to prevent
"Unbalanced IRQ <x> wake disable" warnings from being printed the first
time disable_irq_wake() is called on platforms that run on that code
path.

Fixes: a23aa040 ("net: stmmac: ethtool: Fixed calltrace caused by unbalanced disable_irq_wake calls")
Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20241101-stmmac-unbalanced-wake-single-fix-v1-1-5952524c97f0@collabora.com


Signed-off-by: Paolo Abeni <pabeni@redhat.com>