stm32f103-minimum: Fix a small BUG when reading from output pin. We need a...

stm32f103-minimum: Fix a small BUG when reading from output pin.  We need a different read_ops to read from output pin. This patch fixes the issue:

nsh> gpio -o 0 /dev/gpout1
Driver: /dev/gpout1
  Output pin:    Value=1
  Writing:       Value=0
  Verify:        Value=1

Now:

nsh> gpio -o 0 /dev/gpout1
Driver: /dev/gpout1
  Output pin:    Value=1
  Writing:       Value=0
  Verify:        Value=0