Fix target selector syntax in 'gcc.dg/vect/bb-slp-cond-1.c'

... to restore testing lost in recent
commit r13-3225-gbd9a05594d227cde79a67dc715bd9d82e9c464e9
"amdgcn: vector testsuite tweaks" (for example, x86_64-pc-linux-gnu):

    PASS: gcc.dg/vect/bb-slp-cond-1.c (test for excess errors)
    PASS: gcc.dg/vect/bb-slp-cond-1.c -flto -ffat-lto-objects  scan-tree-dump vect "(no need for alias check [^\\n]* when VF is 1|no alias between [^\\n]* when [^\\n]* is outside \\(-16, 16\\))"
    [-PASS: gcc.dg/vect/bb-slp-cond-1.c -flto -ffat-lto-objects  scan-tree-dump-times vect "loop vectorized" 1-]
    PASS: gcc.dg/vect/bb-slp-cond-1.c -flto -ffat-lto-objects (test for excess errors)
    PASS: gcc.dg/vect/bb-slp-cond-1.c -flto -ffat-lto-objects execution test
    PASS: gcc.dg/vect/bb-slp-cond-1.c execution test
    PASS: gcc.dg/vect/bb-slp-cond-1.c scan-tree-dump vect "(no need for alias check [^\\n]* when VF is 1|no alias between [^\\n]* when [^\\n]* is outside \\(-16, 16\\))"
    [-PASS: gcc.dg/vect/bb-slp-cond-1.c scan-tree-dump-times vect "loop vectorized" 1-]

	gcc/testsuite/
	* gcc.dg/vect/bb-slp-cond-1.c: Fix target selector syntax.

gcc/testsuite/gcc.dg/vect/bb-slp-cond-1.c

@@ -46,6 +46,6 @@ int main ()
 }
 
 /* { dg-final { scan-tree-dump {(no need for alias check [^\n]* when VF is 1|no alias between [^\n]* when [^\n]* is outside \(-16, 16\))} "vect" { target vect_element_align } } } */
-/* { dg-final { scan-tree-dump-times "loop vectorized" 1 "vect" { target { vect_element_align && !amdgcn-*-* } } } } */
+/* { dg-final { scan-tree-dump-times "loop vectorized" 1 "vect" { target { vect_element_align && { ! amdgcn-*-* } } } } } */
 /* { dg-final { scan-tree-dump-times "loop vectorized" 2 "vect" { target amdgcn-*-* } } } */