lmbench: needs mmu

lmbench: needs mmu

Fix below build error:

./tmp./bin/arm/lmbench.a(lib_timing.o): In function `benchmp':
lib_timing.c:(.text+0x34fc): undefined reference to `fork'
collect2: ld returned 1 exit status.
./bin/arm/lmbench.a(lib_tcp.o): In function `tcp_connect/'cc8Ta2C2.o: Inmake[2]:  function `*** [../bin/arm/bw_file_rd] Error 1
initialize':
lib_tcp.c:make[2]: (.text+0x208): warning: gethostbyname*** Waiting for unfinished jobs....
 is obsolescent, use: getnameinfo
bw_pipe.c(): (instead..text
/+tmp0x134/)cc5yg1Q2.o: :undefined In  referencefunction  to`server_main `'fork:
'bw_tcp.c
.:.(./textbin+/0x298arm)/:lmbench.a (undefinedlib_timing.o )reference:  Into  function`fork '`
benchmp/'tmp:/
cc5yg1Q2.olib_timing.c:: (In.text function+0x34fc `)main: 'undefined:
 bw_tcp.creference: (to. text`fork+0x370'
)collect2: : undefined reference to `fork'
../bin/armld returned 1 exit status/lmbench.a(lib_timing.o): In function
`benchmp':
lib_timing.c:(.text+0x34fc): undefined reference to `fork'
collect2: ld returned 1 exit status
make[2]: *** [../bin/arm/bw_pipe] Error 1
make[2]: *** [../bin/arm/bw_tcp] Error 1
../bin/arm/lmbench.a(lib_timing.o): In function `benchmp':
lib_timing.c:(.text+0x34fc): undefined reference to `fork'
collect2: ld returned 1 exit status
make[2]: *** [../bin/arm/bw_mmap_rd] Error 1
../bin/arm/lmbench.a(lib_timing.o): In function `benchmp':
lib_timing.c:(.text+0x34fc): undefined reference to `fork'
collect2: ld returned 1 exit status
make[2]: *** [../bin/arm/bw_mem] Error 1

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>