mtd: devices: Add new Pagescope read feature for sdxprairie

Add new enhanced read page feature 'Pagescope Read' support
for sdxprairie.

In QPIC v1, SW is needed to write EXEC_CMD register for each
Code word and collect any Status related to that CW before
issuing EXEC_CMD for next CW.

With Page scope command (Supported In QPIC v2 and higher),
currently supported only for read commands in bam mode, is
truly a page mode command where SW is required to  issue
EXEC_CMD only once for a page. Controller HW takes care of
Codeword specific details and automatically returns status
associated with each CW to BAM pipe, dedicated for status
deposition.

With this command, SW now can issue one read command for a
page and upon receiving completion interrupt, can process
status, that have already been deposited in memory through
status BAM pipe.

Below are the KPI values taken for 1GB reads
with/without Pagescope-read feature.

| With PS-read  | Without PS-read |      Diff(%)      |
|  26.59 sec.   |   29.40 sec.    | 2.81 sec.(10.56%) |
|  37.6 MB/s    |   34.0 MB/s     | 3.6 MB/s (10.58%) |.

Change-Id: I0380b46320861876b6b33b059caf2f966c13192a
Signed-off-by: Pradeep P V K <ppvk@codeaurora.org>