ARM: dts: mmp3: Fix USB & USB PHY node names

There are better generic ones and the validation is going to complain:

  mmp3-dell-ariel.dt.yaml: hsic@f0001000: $nodename:0: 'hsic@f0001000'
      does not match '^usb(@.*)?'
  mmp3-dell-ariel.dt.yaml: hsic@f0002000: $nodename:0: 'hsic@f0002000'
      does not match '^usb(@.*)?'
  ...

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>