Fix length attribute for casesi_load pattern.

Perl compilation was broken:
--->---
$ arc-linux-gcc -DPERL_CORE -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -matomic -pipe -mdiv-rem -Os   -c -o perl.o perl.c
perl.s: Assembler messages:
perl.s:1271: Error: operand out of range (512 is not between -512 and 511)
--->---

Fix is taken from current development branch of GCC for ARC and will be a
part of the next release of ARC tools, so at that point patch should be dropped.

https://github.com/foss-for-synopsys-dwc-arc-processors/gcc/commit/664ccd8d5ac8e047faac599309c9c2867af3a736

Signed-off-by: Claudiu Zissulescu <claziss@synopsys.com>
---

--- a/gcc/config/arc/arc.md
+++ b/gcc/config/arc/arc.md
@@ -3834,22 +3834,8 @@
     }
 }"
   [(set_attr "type" "load")
-   (set_attr_alternative "iscompact"
-     [(cond
-	[(ne (symbol_ref "GET_MODE (PATTERN (next_real_insn (operands[3])))")
-	     (symbol_ref "QImode"))
-	 (const_string "false")
-	 (match_test "!ADDR_DIFF_VEC_FLAGS (PATTERN (next_real_insn (operands[3]))).offset_unsigned")
-	 (const_string "false")]
-	(const_string "true"))
-      (const_string "false")
-      (const_string "false")])
-   (set_attr_alternative "length"
-     [(cond
-	[(eq_attr "iscompact" "false") (const_int 4)]
-	(const_int 2))
-      (const_int 4)
-      (const_int 8)])])
+   (set_attr "iscompact" "false")
+   (set_attr "length" "4,4,8")])
 
 ; Unlike the canonical tablejump, this pattern always uses a jump address,
 ; even for CASE_VECTOR_PC_RELATIVE.