testsuite: fix target-specific 'do-' typos

Fix some target-specific 'do-' (rather than 'dg-') typos.

gcc/testsuite/ChangeLog:

	* gcc.target/m68k/pr108640.c: Fix dg directive typo.
	* gcc.target/m68k/pr110934.c: Ditto.
	* gcc.target/m68k/pr82420.c: Ditto.
	* gcc.target/powerpc/pr99708.c: Ditto.

gcc/testsuite/gcc.target/m68k/pr108640.c

@@ -1,5 +1,5 @@
 /* { dg-do compile } */
-/* { do-options "-O1" } */
+/* { dg-options "-O1" } */
 
 int x;
 void andsi3(void) { x &= ~(1 << 16); }

gcc/testsuite/gcc.target/m68k/pr110934.c

@@ -1,5 +1,5 @@
 /* { dg-do compile } */
-/* { do-options "-fzero-call-used-regs=used -fpic -O2" } */
+/* { dg-options "-fzero-call-used-regs=used -fpic -O2" } */
 
 extern double clobber_fp0 (void);
 

gcc/testsuite/gcc.target/m68k/pr82420.c

@@ -1,4 +1,4 @@
-/* { do-do compile } */
+/* { dg-do compile } */
 /* { dg-options "-march=68000 -malign-int" } */
 
 int a;

gcc/testsuite/gcc.target/powerpc/pr99708.c

@@ -1,6 +1,6 @@
 /* { dg-do run } */
 /* { dg-skip-if "" { powerpc*-*-darwin* powerpc-ibm-aix* } } */
-/* { require-effective-target ppc_float128_sw } */
+/* { dg-require-effective-target ppc_float128_sw } */
 /* { dg-options "-O2 -mvsx -mfloat128" } */
 
 /*