staging: mt7621-pci: avoid use 'err' local variable

staging: mt7621-pci: avoid use 'err' local variable

Function 'mt7621_pcie_request_resources' is using 'err'
local variable to get value returned from 'devm_request_pci_bus_resources'
and returning after that. This is not needed at all. Instead of that
just directly return returned value by the function which is also
returning zero on success.

Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Link: https://lore.kernel.org/r/20190720072908.16795-1-sergio.paracuellos@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>