dmaengine: dw-edma: Fix unaligned 64bit access

dmaengine: dw-edma: Fix unaligned 64bit access

On some arch (ie aarch64 iMX8MM) unaligned PCIe accesses are
not allowed and lead to a kernel Oops.
  [ 1911.668835] Unable to handle kernel paging request at virtual address ffff80001bc00a8c
  [ 1911.668841] Mem abort info:
  [ 1911.668844]   ESR = 0x96000061
  [ 1911.668847]   EC = 0x25: DABT (current EL), IL = 32 bits
  [ 1911.668850]   SET = 0, FnV = 0
  [ 1911.668852]   EA = 0, S1PTW = 0
  [ 1911.668853] Data abort info:
  [ 1911.668855]   ISV = 0, ISS = 0x00000061
  [ 1911.668857]   CM = 0, WnR = 1
  [ 1911.668861] swapper pgtable: 4k pages, 48-bit VAs, pgdp=0000000040ff4000
  [ 1911.668864] [ffff80001bc00a8c] pgd=00000000bffff003, pud=00000000bfffe003, pmd=0068000018400705
  [ 1911.668872] Internal error: Oops: 96000061 [#1] PREEMPT SMP
  ...

The llp register present in the channel group registers is not
aligned on 64bit.

Fix unaligned 64bit access using two 32bit accesses

Fixes: 04e0a39fc10f ("dmaengine: dw-edma: Add writeq() and readq() for 64 bits architectures")
Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Link: https://lore.kernel.org/r/20220225120252.309404-1-herve.codina@bootlin.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>