powerpc: sysdev: cpm: fix gpio save_regs functions

of_mm_gpiochip_add_data() calls mm_gc->save_regs() before
setting the data. Therefore ->save_regs() cannot use
gpiochip_get_data()

[    0.275940] Unable to handle kernel paging request for data at address 0x00000130
[    0.283120] Faulting instruction address: 0xc01b44cc
[    0.288175] Oops: Kernel access of bad area, sig: 11 [#1]
[    0.293343] PREEMPT CMPC885
[    0.296141] CPU: 0 PID: 1 Comm: swapper Not tainted 4.7.0-g65124df-dirty #68
[    0.304131] task: c6074000 ti: c6080000 task.ti: c6080000
[    0.309459] NIP: c01b44cc LR: c0011720 CTR: c0011708
[    0.314372] REGS: c6081d90 TRAP: 0300   Not tainted  (4.7.0-g65124df-dirty)
[    0.322267] MSR: 00009032 <EE,ME,IR,DR,RI>  CR: 24000028  XER: 20000000
[    0.328813] DAR: 00000130 DSISR: c0000000
GPR00: c01b6d0c c6081e40 c6074000 c6017000 c9028000 c601d028 c6081dd8 00000000
GPR08: c601d028 00000000 ffffffff 00000001 24000044 00000000 c0002790 00000000
GPR16: 00000000 00000000 00000000 00000000 00000000 00000000 c05643b0 00000083
GPR24: c04a1a6c c0560000 c04a8308 c04c6480 c0012498 c6017000 c7ffcc78 c6017000
[    0.360806] NIP [c01b44cc] gpiochip_get_data+0x4/0xc
[    0.365684] LR [c0011720] cpm1_gpio16_save_regs+0x18/0x44
[    0.370972] Call Trace:
[    0.373451] [c6081e50] [c01b6d0c] of_mm_gpiochip_add_data+0x70/0xdc
[    0.379624] [c6081e70] [c00124c0] cpm_init_par_io+0x28/0x118
[    0.385238] [c6081e80] [c04a8ac0] do_one_initcall+0xb0/0x17c
[    0.390819] [c6081ef0] [c04a8cbc] kernel_init_freeable+0x130/0x1dc
[    0.396924] [c6081f30] [c00027a4] kernel_init+0x14/0x110
[    0.402177] [c6081f40] [c000b424] ret_from_kernel_thread+0x5c/0x64
[    0.408233] Instruction dump:
[    0.411168] 4182fafc 3f80c040 48234c6d 3bc0fff0 3b9c5ed0 4bfffaf4 81290020 712a0004
[    0.418825] 4182fb34 48234c51 4bfffb2c 81230004 <80690130> 4e800020 7c0802a6 9421ffe0
[    0.426763] ---[ end trace fe4113ee21d72ffa ]---

fixes: e65078f1 ("powerpc: sysdev: cpm1: use gpiochip data pointer")
fixes: a14a2d48 ("powerpc: cpm_common: use gpiochip data pointer")
Cc: stable@vger.kernel.org
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>