PPC: Use r2 instead of r29 as global data pointer

R29 was an unlucky choice as with recent toolchains (gcc-4.2.x) gcc
will refuse to use load/store multiple insns; instead, it issues a
list of simple load/store instructions upon function entry and exit,
resulting in bigger code size, which in turn makes the build for a
few boards fail.

Use r2 instead.

Signed-off-by: Wolfgang Denk <wd@denx.de>

examples/stubs.c

@@ -25,14 +25,14 @@ gd_t *global_data;
 	: : "i"(XF_ ## x * sizeof(void *)) : "eax", "ecx");
 #elif defined(CONFIG_PPC)
 /*
- * r29 holds the pointer to the global_data, r11 is a call-clobbered
+ * r2 holds the pointer to the global_data, r11 is a call-clobbered
  * register
  */
 #define EXPORT_FUNC(x) \
 	asm volatile (			\
 "	.globl " #x "\n"		\
 #x ":\n"				\
-"	lwz	%%r11, %0(%%r29)\n"	\
+"	lwz	%%r11, %0(%%r2)\n"	\
 "	lwz	%%r11, %1(%%r11)\n"	\
 "	mtctr	%%r11\n"		\
 "	bctr\n"				\

examples/test_burst_lib.S

@@ -70,7 +70,7 @@ mmu_init:
 	 * we can load the instruction and data TLB registers with the
 	 * same values.
 	 */
-	lwz	r9,20(r29)		/* gd->ram_size */
+	lwz	r9,20(r2)		/* gd->ram_size */
 	addis	r9,r9,-0x80
 
 	mr	r8, r9			/* Higher 8 Meg in SDRAM */

examples/x86-testapp.c

@@ -30,11 +30,11 @@ asm volatile (						\
 asm volatile (						\
 "	.globl mon_" #x "\n"				\
 "mon_" #x ":\n"						\
-"	lwz	%%r11, %0(%%r29)\n"			\
+"	lwz	%%r11, %0(%%r2)\n"			\
 "	lwz	%%r11, %1(%%r11)\n"			\
 "	mtctr	%%r11\n"				\
 "	bctr\n"					\
-	: : "i"(offsetof(xxx_t, pfunc)), "i"(XF_ ## x * sizeof(void *)) : "r11", "r29");
+	: : "i"(offsetof(xxx_t, pfunc)), "i"(XF_ ## x * sizeof(void *)) : "r11", "r2");
 #elif defined(__arm__)
 #define EXPORT_FUNC(x)					\
 asm volatile (						\
@@ -67,7 +67,7 @@ int main(void)
 #if defined(__i386__)
 	xxx_t *pq;
 #elif defined(__powerpc__)
-	register volatile xxx_t *pq asm("r29");
+	register volatile xxx_t *pq asm("r2");
 #elif defined(__arm__)
 	register volatile xxx_t *pq asm("r8");
 #elif defined(__mips__)