net: stmmac: Convert open-coded register polling to helper macro

net: stmmac: Convert open-coded register polling to helper macro

Drop the open-coded register polling routines.
Use readl_poll_timeout_atomic() in atomic state.

Also adjust the delay time to 10us which seems more reasonable.

Tested on NXP i.MX8MP and ROCKCHIP RK3588 boards,
the break condition was met right after the first polling,
no delay involved at all.
So the 10us delay should be long enough for most cases.

Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Furong Xu <0x1207@gmail.com>
Link: https://patch.msgid.link/20250927081036.10611-1-0x1207@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>