test/hello_world: Fix makefile rule
test/hello_world: Fix makefile rule

powerpc-linux-gnu-gcc -m64 -c -MMD -Itest/hello_world/hello_kernel/ -o
   test/hello_world/hello_kernel/hello_kernel.o
   test/hello_world/hello_kernel/hello_kernel.S
   test/hello_world/hello_kernel/asm-utils.h
 powerpc-linux-gnu-gcc: fatal error: cannot specify -o with -c, -S or -E
   with multiple files

GCC barfed as we were passing the header and the c file while compiling
with -c. Fix the rule to just build source file.

Signed-off-by: Joel Stanley <4816dabf8db1bc6cac35b3a24cab2ff844b5b0c7@jms.id.au>
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

cyrilbur-ibm/skiboot,apopple/skiboot,open-power/skiboot,qemu/skiboot,ddstreet/skiboot,apopple/skiboot,neelegup/skiboot,open-power/skiboot,mikey/skiboot,shenki/skiboot,stewart-ibm/skiboot,shenki/skiboot,csmart/skiboot,qemu/skiboot,jk-ozlabs/skiboot,neelegup/skiboot,open-power/skiboot,cyrilbur-ibm/skiboot,qemu/skiboot,mikey/skiboot,csmart/skiboot,neelegup/skiboot,legoater/skiboot,stewart-ibm/skiboot,legoater/skiboot,shenki/skiboot,cyrilbur-ibm/skiboot,jk-ozlabs/skiboot,apopple/skiboot,qemu/skiboot,mikey/skiboot,open-power/skiboot,qemu/skiboot,ddstreet/skiboot,jk-ozlabs/skiboot,legoater/skiboot,open-power/skiboot,shenki/skiboot,shenki/skiboot,stewart-ibm/skiboot,legoater/skiboot,legoater/skiboot,ddstreet/skiboot,csmart/skiboot