linux-user: Adjust comment to reflect the code.

If the user didn't specify reserved_va, there's an else for 64-bit host
32-bit (or fewer) target to reserve 32-bits of address space. Update the
comments to reflect this, and rejustify comment to 80 columns.

Signed-off-by: Warner Losh <imp@bsdimp.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

linux-user/main.c

@@ -814,10 +814,10 @@ int main(int argc, char **argv, char **envp)
     thread_cpu = cpu;
 
     /*
-     * Reserving too much vm space via mmap can run into problems
-     * with rlimits, oom due to page table creation, etc.  We will
-     * still try it, if directed by the command-line option, but
-     * not by default.
+     * Reserving too much vm space via mmap can run into problems with rlimits,
+     * oom due to page table creation, etc.  We will still try it, if directed
+     * by the command-line option, but not by default. Unless we're running a
+     * target address space of 32 or fewer bits on a host with 64 bits.
      */
     max_reserved_va = MAX_RESERVED_VA(cpu);
     if (reserved_va != 0) {