Merge branch 'fix-some-bugs-in-stmmac'

Biao Huang says:

====================
fix some bugs in stmmac

changes in v4:
        since MTL_OPERATION_MODE write back issue has be fixed in the latest driver,
remove original patch#3

changes in v3:
        add a Fixes:tag for each patch

changes in v2:
        1. update rx_tail_addr as Jose's comment
        2. changes clk_csr condition as Alex's proposition
        3. remove init lines in dwmac-mediatek, get clk_csr from dts instead.

v1:
This series fix some bugs in stmmac driver
3 patches are for common stmmac or dwmac4:
        1. update rx tail pointer to fix rx dma hang issue.
        2. change condition for mdc clock to fix csr_clk can't be zero issue.
        3. write the modified value back to MTL_OPERATION_MODE.
1 patch is for dwmac-mediatek:
        modify csr_clk value to fix mdio read/write fail issue for dwmac-mediatek
====================

Signed-off-by: David S. Miller <davem@davemloft.net>