perf probe: Change MAX_CMDLEN

perf probe: Change MAX_CMDLEN

There are many SDT markers in powerpc whose uprobe definition goes
beyond current MAX_CMDLEN, especially when target filename is long and
sdt marker has long list of arguments. For example, definition of sdt
marker

  method__compile__end: 8@17 8@9 8@10 -4@8 8@7 -4@6 8@5 -4@4 1@37(28)

from file

  /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.91-2.b14.fc22.ppc64/jre/lib/ppc64/server/libjvm.so

is

  p:sdt_hotspot/method__compile__end /usr/lib/jvm/java-1.8.0-openjdk-\
    1.8.0.91-2.b14.fc22.ppc64/jre/lib/ppc64/server/libjvm.so:0x4c4e00\
    arg1=%gpr17:u64 arg2=%gpr9:u64 arg3=%gpr10:u64 arg4=%gpr8:s32\
    arg5=%gpr7:u64 arg6=%gpr6:s32 arg7=%gpr5:u64 arg8=%gpr4:s32\
    arg9=+37(%gpr28):u8

'perf probe' fails with segfault for such markers. As the uprobe_events
file accepts definitions up to 4094 characters(4096 - 2 (\n\0)),
increase value of MAX_CMDLEN match that.

Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexis Berlemont <alexis.berlemont@gmail.com>
Cc: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20170207054547.3690-1-ravi.bangoria@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>