staging: mt7621-pci: replace 'mdelay()' with 'msleep()'

Function 'mt7621_pcie_init_ports' is never called in atomic context.
It calls mdelay() to busily wait, which is not necessary. mdelay()
can be replaced with msleep().

Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>