sh: unwinder: Set the flags for DW_CFA_val_offset ops as DWARF_VAL_OFFSET

The handling of DW_CFA_val_offset ops was incorrectly using the
DWARF_REG_OFFSET flag but the register's value cannot be calculated
using the DWARF_REG_OFFSET method. Create a new flag to indicate that a
different method must be used to calculate the register's value even
though there is no implementation for DWARF_VAL_OFFSET yet; it's mainly
just a place holder.
Signed-off-by: Matt Fleming <matt@console-pimps.org>

arch/sh/include/asm/dwarf.h

@@ -296,6 +296,7 @@ struct dwarf_reg {
 	unsigned long addr;
 	unsigned long flags;
 #define DWARF_REG_OFFSET	(1 << 0)
+#define DWARF_VAL_OFFSET	(1 << 1)
 };
 
 /*

arch/sh/kernel/dwarf.c

@@ -11,6 +11,7 @@
  *
  * TODO:
  *	- DWARF64 doesn't work.
+ *	- Registers with DWARF_VAL_OFFSET rules aren't handled properly.
  */
 
 /* #define DEBUG */
@@ -499,7 +500,7 @@ static int dwarf_cfa_execute_insns(unsigned char *insn_start,
 			count = dwarf_read_leb128(current_insn, &offset);
 			offset *= cie->data_alignment_factor;
 			regp = dwarf_frame_alloc_reg(frame, reg);
-			regp->flags |= DWARF_REG_OFFSET;
+			regp->flags |= DWARF_VAL_OFFSET;
 			regp->addr = offset;
 			break;
 		case DW_CFA_GNU_args_size: