memory: renesas-rpc-if: Correct QSPI data transfer in Manual mode

This patch fixes 2 problems:
[1] The output warning logs and data loss when performing
mount/umount then remount the device with jffs2 format.
[2] The access width of SMWDR[0:1]/SMRDR[0:1] register is wrong.

This is the sample warning logs when performing mount/umount then
remount the device with jffs2 format:
jffs2: jffs2_scan_inode_node(): CRC failed on node at 0x031c51d4:
Read 0x00034e00, calculated 0xadb272a7

The reason for issue [1] is that the writing data seems to
get messed up.
Data is only completed when the number of bytes is divisible by 4.
If you only have 3 bytes of data left to write, 1 garbage byte
is inserted after the end of the write stream.
If you only have 2 bytes of data left to write, 2 bytes of '00'
are added into the write stream.
If you only have 1 byte of data left to write, 2 bytes of '00'
are added into the write stream. 1 garbage byte is inserted after
the end of the write stream.

To solve problem [1], data must be written continuously in serial
and the write stream ends when data is out.

Following HW manual 62.2.15, access to SMWDR0 register should be
in the same size as the transfer size specified in the SPIDE[3:0]
bits in the manual mode enable setting register (SMENR).
Be sure to access from address 0.

So, in 16-bit transfer (SPIDE[3:0]=b'1100), SMWDR0 should be
accessed by 16-bit width.
Similar to SMWDR1, SMDDR0/1 registers.
In current code, SMWDR0 register is accessed by regmap_write()
that only set up to do 32-bit width.

To solve problem [2], data must be written 16-bit or 8-bit when
transferring 1-byte or 2-byte.

Fixes: ca7d8b98 ("memory: add Renesas RPC-IF driver")
Cc: <stable@vger.kernel.org>
Signed-off-by: Duc Nguyen <duc.nguyen.ub@renesas.com>
[wsa: refactored to use regmap only via reg_read/reg_write]
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Link: https://lore.kernel.org/r/20210922091007.5516-1-wsa+renesas@sang-engineering.com


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>