FROMLIST: lib: sparse: allocate blkcnt instead of arbitrary small number

Commit 62649165 ("lib: sparse: Make CHUNK_TYPE_RAW buffer aligned") fixed cache alignment for systems with a D-CACHE.

However it introduced some performance regressions [1] on system flashing huge images, such as Android.

On AM62x SK EVM, we also observe such performance penalty:
Sending sparse 'super' 1/2 (768793 KB)             OKAY [ 23.954s]
Writing 'super'                                    OKAY [ 75.926s]
Sending sparse 'super' 2/2 (629819 KB)             OKAY [ 19.641s]
Writing 'super'                                    OKAY [ 62.849s]
Finished. Total time: 182.474s

The reason for this is that we use an arbitrary small buffer (info->blksz * 100) for transferring.

Fix it by using a bigger buffer (info->blksz * blkcnt) as suggested in the original's patch review [2].

With this patch, performance impact is mitigated:

Sending sparse 'super' 1/2 (768793 KB)             OKAY [ 24.006s]
Writing 'super'                                    OKAY [ 15.920s]
Sending sparse 'super' 2/2 (629819 KB)             OKAY [ 19.651s]
Writing 'super'                                    OKAY [ 14.665s]
Finished. Total time: 74.346s

[1] https://lore.kernel.org/r/20221118121323.4009193-1-gary.bisson@boundarydevices.com [2] https://lore.kernel.org/r/all/43e4c17c-4483-ec8e-f843-9b4c5569bd18@seco.com/

Fixes: 62649165 ("lib: sparse: Make CHUNK_TYPE_RAW buffer aligned") Signed-off-by: Mattijs Korpershoek mkorpershoek@baylibre.com (am from https://patchwork.ozlabs.org/patch/1795904/) (also found at https://lore.kernel.org/r/20230616-sparse-flash-fix-v1-1-6bafeacc567b@baylibre.com)