Update directories for new name of TF-A directories

The TF-A URL was updated, as a result the name of the
directory changed as part of the new git URL and not
all the referenced directories were updated.

Fixes: 0ec0207fe07 ("Update the ARM trusted firmware git URL")
Signed-off-by: Peter Robinson <pbrobinson@gmail.com>
diff --git a/doc/board/hisilicon/hikey960.rst b/doc/board/hisilicon/hikey960.rst
index f726fc7..de846f6 100644
--- a/doc/board/hisilicon/hikey960.rst
+++ b/doc/board/hisilicon/hikey960.rst
@@ -64,7 +64,7 @@
 
 .. code-block:: bash
 
-  cd ~/hikey960/src/arm-trusted-firmware
+  cd ~/hikey960/src/trusted-firmware-a
   make CROSS_COMPILE=aarch64-linux-gnu- all fip \
     SCP_BL2=~/hikey960/bin/lpm3.img \
     BL33=~/hikey960/bin/u-boot.bin DEBUG=1 PLAT=hikey960
@@ -81,9 +81,9 @@
 .. code-block:: bash
 
   cd ~/hikey960/src/l-loader
-  ln -sf ~/hikey960/src/arm-trusted-firmware/build/hikey960/debug/bl1.bin
-  ln -sf ~/hikey960/src/arm-trusted-firmware/build/hikey960/debug/bl2.bin
-  ln -sf ~/hikey960/src/arm-trusted-firmware/build/hikey960/debug/fip.bin
+  ln -sf ~/hikey960/src/trusted-firmware-a/build/hikey960/debug/bl1.bin
+  ln -sf ~/hikey960/src/trusted-firmware-a/build/hikey960/debug/bl2.bin
+  ln -sf ~/hikey960/src/trusted-firmware-a/build/hikey960/debug/fip.bin
   ln -sf ~/hikey960/bin/u-boot.bin
   make hikey960 PTABLE_LST=linux-32g NS_BL1U=u-boot.bin