bpf: Fix warning for cast from restricted gfp_t in verifier

This fixes the sparse warning reported by the kernel test robot:

kernel/bpf/verifier.c:13499:47: sparse: warning: cast from restricted gfp_t
kernel/bpf/verifier.c:13501:47: sparse: warning: cast from restricted gfp_t

This fix can be verified locally by running:
1) wget
https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross
-O make.cross

2) chmod +x ~/bin/make.cross

3) COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 ./make.cross
C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__'

Fixes: b00fa38a ("bpf: Enable non-atomic allocations in local storage")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220321185802.824223-1-joannekoong@fb.com

kernel/bpf/verifier.c

@@ -13496,9 +13496,9 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
 		    insn->imm == BPF_FUNC_sk_storage_get ||
 		    insn->imm == BPF_FUNC_inode_storage_get) {
 			if (env->prog->aux->sleepable)
-				insn_buf[0] = BPF_MOV64_IMM(BPF_REG_5, (__s32)GFP_KERNEL);
+				insn_buf[0] = BPF_MOV64_IMM(BPF_REG_5, (__force __s32)GFP_KERNEL);
 			else
-				insn_buf[0] = BPF_MOV64_IMM(BPF_REG_5, (__s32)GFP_ATOMIC);
+				insn_buf[0] = BPF_MOV64_IMM(BPF_REG_5, (__force __s32)GFP_ATOMIC);
 			insn_buf[1] = *insn;
 			cnt = 2;