README.hardware.md: Fix the tftp example

There is a double 'tftp' command in the example for loading
vmlinux via tftp command in U-Boot.

Fix it by removing the extra occurrence.

(From meta-yocto rev: 60f5479ffcde1036899826db01506e981f90e360)

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta-yocto-bsp/README.hardware.md

@@ -203,7 +203,7 @@ Load the kernel, and boot the system as follows:
 
  5. Download the kernel and boot:
 
- => tftp tftp $loadaddr vmlinux
+ => tftp $loadaddr vmlinux
  => bootoctlinux $loadaddr coremask=0x3 root=/dev/nfs rw nfsroot=<nfsroot ip>:<rootfs path> ip=<board ip>:<server ip>:<gateway ip>:<netmask>:edgerouter:eth0:off mtdparts=phys_mapped_flash:512k(boot0),512k(boot1),64k@3072k(eeprom)
 
 --- Booting from USB disk ---