staging: mt7621-pci: replace mdelay with msleep

staging: mt7621-pci: replace mdelay with msleep

There are two mdelay calls in driver code located in
'mt7621_pcie_reset_assert' and 'mt7621_pcie_reset_rc_deassert'
functions. Both of them are not called in an interrupt handler
nor holding any spinlock. Hence, the function mdelay in them
can be replaced with msleep, to reduce busy wait.

Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Link: https://lore.kernel.org/r/20210505121736.6459-6-sergio.paracuellos@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>