rsi: fix kernel panic observed on 64bit machine

Following kernel panic is observed on 64bit machine while loading
the driver. It is fixed if we pass dynamically allocated memory to
SDIO for DMA.

BUG: unable to handle kernel paging request at ffffeb04000172e0
IP: sg_miter_stop+0x56/0x70
PGD 0 P4D 0
Oops: 0000 [#1] SMP PTI
Modules linked in: rsi_sdio(OE+) rsi_91x(OE) btrsi(OE) rfcomm bluetooth
ecdh_generic mac80211 mmc_block fuse xt_CHECKSUM iptable_mangle
drm_kms_helper mmc_core serio_raw drm firewire_ohci tg3
CPU: 0 PID: 4003 Comm: insmod Tainted: G           OE    4.16.0-rc1+ #27
Hardware name: Dell Inc. Latitude E5500                  /0DW634, BIOS
A19 06/13/2013
RIP: 0010:sg_miter_stop+0x56/0x70
RSP: 0018:ffff88007d003e78 EFLAGS: 00010002
RAX: 0000000000000003 RBX: 0000000000000004 RCX: 0000000000000000
RDX: ffffeb04000172c0 RSI: ffff88002f58002c RDI: ffff88007d003e80
RBP: 0000000000000004 R08: ffff88007d003e80 R09: 0000000000000008
R10: 0000000000000003 R11: 0000000000000001 R12: 0000000000000004
R13: ffff88002f580028 R14: 0000000000000000 R15: 0000000000000004
FS:  00007f35c29db700(0000) GS:ffff88007d000000(0000)
knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffeb04000172e0 CR3: 000000007038e000 CR4: 00000000000406f0
Call Trace:
<IRQ>
sg_copy_buffer+0xc6/0xf0
sdhci_tasklet_finish+0x170/0x260 [sdhci]
tasklet_action+0xf4/0x100
__do_softirq+0xef/0x26e
irq_exit+0xbe/0xd0
do_IRQ+0x4a/0xc0
common_interrupt+0xa2/0xa2
</IRQ>

Signed-off-by: Amitkumar Karwar <amit.karwar@redpinesignals.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>