drivers/bcm2835gpio: fix build for ARM host

drivers/bcm2835gpio: fix build for ARM host

The commit 84ca4995adfa ("drivers/bcm2835gpio: fix usage messages")
has been merged before commit 6cb5ba6f1136 ("helper/command: change
prototype of command_print/command_print_sameline") introducing two
new call to command_print() that were not modified by the second
commit.
This triggers a compile error on ARM host.

Fix the incorrect function call.

Change-Id: I2736bae24141685b7590fd6b4aa5e6a29b2cab29
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/5174
Tested-by: jenkins