mm/mmap.c: remove unnecessary local variable

The local variable 'retval' is assigned just for once in __do_sys_brk(),
and the function returns the value of the local variable right after the
assignment.  Remove unnecessary assignment and local variable declaration.

Link: https://lkml.kernel.org/r/20201222103249.30683-1-adrianhuang0701@gmail.com
Signed-off-by: Adrian Huang <ahuang12@lenovo.com>
Acked-by: Souptick Joarder <jrdr.linux@gmail.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/mmap.c

@@ -189,7 +189,6 @@ static int do_brk_flags(unsigned long addr, unsigned long request, unsigned long
 		struct list_head *uf);
 SYSCALL_DEFINE1(brk, unsigned long, brk)
 {
-	unsigned long retval;
 	unsigned long newbrk, oldbrk, origbrk;
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *next;
@@ -281,9 +280,8 @@ success:
 	return brk;
 
 out:
-	retval = origbrk;
 	mmap_write_unlock(mm);
-	return retval;
+	return origbrk;
 }
 
 static inline unsigned long vma_compute_gap(struct vm_area_struct *vma)