rtw88: pci: remove set but not used variable 'ip_sel'

rtw88: pci: remove set but not used variable 'ip_sel'

BugLink: https://bugs.launchpad.net/bugs/1838133
Fixes gcc '-Wunused-but-set-variable' warning:

drivers/net/wireless/realtek/rtw88/pci.c: In function 'rtw_pci_phy_cfg':
drivers/net/wireless/realtek/rtw88/pci.c:993:6: warning:
 variable 'ip_sel' set but not used [-Wunused-but-set-variable]

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
(cherry picked from commit d1b68c1182380e50cad4b7bd76ee68f64951a64b linux-next)
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>