igc: Remove unused igc_read/write_pcie_cap_reg

The last uses of igc_read_pcie_cap_reg() and igc_write_pcie_cap_reg()
were removed in 2019 by
commit 16ecd8d9 ("igc: Remove the obsolete workaround")

Remove them.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Reviewed-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Link: https://patch.msgid.link/20250102174142.200700-4-linux@treblig.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>