Revert "arm64: jump_label: use constraints "Si" instead of "i""

This reverts commit f9daab0.

Geert reports that his particular GCC 5.5 vintage toolchain fails to
build an arm64 defconfig because of this change:

 |    arch/arm64/include/asm/jump_label.h:25:2: error: invalid 'asm':
 | invalid operand
 |     asm goto(
      ^
Aopparently, this is something we claim to support, so let's revert back
to the old jump label constraint for now while discussions about raising
the minimum GCC version are ongoing.

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/r/CAMuHMdX+6fnAf8Hm6EqYJPAjrrLO9T7c=Gu3S8V_pqjSDowJ6g@mail.gmail.com
Signed-off-by: Will Deacon <will@kernel.org>

Author: willdeacon

arch/arm64/include/asm/jump_label.h

@@ -15,10 +15,6 @@
 
 #define JUMP_LABEL_NOP_SIZE		AARCH64_INSN_SIZE
 
-/*
- * Prefer the constraint "S" to support PIC with GCC. Clang before 19 does not
- * support "S" on a symbol with a constant offset, so we use "i" as a fallback.
- */
 static __always_inline bool arch_static_branch(struct static_key * const key,
 					       const bool branch)
 {
@@ -27,9 +23,9 @@ static __always_inline bool arch_static_branch(struct static_key * const key,
 		 "	.pushsection	__jump_table, \"aw\"	\n\t"
 		 "	.align		3			\n\t"
 		 "	.long		1b - ., %l[l_yes] - .	\n\t"
-		 "	.quad		(%[key] - .) + %[bit0]  \n\t"
+		 "	.quad		%c0 - .			\n\t"
 		 "	.popsection				\n\t"
-		 :  :  [key]"Si"(key), [bit0]"i"(branch) :  : l_yes);
+		 :  :  "i"(&((char *)key)[branch]) :  : l_yes);
 
 	return false;
 l_yes:
@@ -44,9 +40,9 @@ static __always_inline bool arch_static_branch_jump(struct static_key * const ke
 		 "	.pushsection	__jump_table, \"aw\"	\n\t"
 		 "	.align		3			\n\t"
 		 "	.long		1b - ., %l[l_yes] - .	\n\t"
-		 "	.quad		(%[key] - .) + %[bit0]  \n\t"
+		 "	.quad		%c0 - .			\n\t"
 		 "	.popsection				\n\t"
-		 :  :  [key]"Si"(key), [bit0]"i"(branch) :  : l_yes);
+		 :  :  "i"(&((char *)key)[branch]) :  : l_yes);
 
 	return false;
 l_yes: