arm64: asm-offsets: add S_FP

So that assembly code can more easily manipulate the FP (x29) within a
pt_regs, add an S_FP asm-offsets definition.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Torsten Duwe <duwe@suse.de>
Tested-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Tested-by: Torsten Duwe <duwe@suse.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>

Author: Mark Rutland

arch/arm64/kernel/asm-offsets.c

@@ -56,6 +56,7 @@ int main(void)
   DEFINE(S_X24,			offsetof(struct pt_regs, regs[24]));
   DEFINE(S_X26,			offsetof(struct pt_regs, regs[26]));
   DEFINE(S_X28,			offsetof(struct pt_regs, regs[28]));
+  DEFINE(S_FP,			offsetof(struct pt_regs, regs[29]));
   DEFINE(S_LR,			offsetof(struct pt_regs, regs[30]));
   DEFINE(S_SP,			offsetof(struct pt_regs, sp));
   DEFINE(S_PSTATE,		offsetof(struct pt_regs, pstate));