fix(pxp): fix issues in pxp cache management callback

[hpfaz]

Description of the feature or fix

fix _invalidate_cache wrong signature in declaration
fix _invalidate_cache uses draw_buf as a data buffer
fix _invalidate_cache uses unknown DEMO_CleanInvalidateCacheByAddr instead of DCACHE_CleanInvalidateByRange
update the *invalidate_cache* functions signature to make draw_buf a pointer to const

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[XuNeo]

Hi,
Thank you for the fix. Could you explain why need to add const to draw_buf?

[hpfaz]

Hi @XuNeo,

I added the 'const' because in lv_draw_pxp_layer draw_buf is declared as follows :
const lv_draw_buf_t * draw_buf = layer_to_draw->draw_buf;
and then used in:
lv_draw_buf_invalidate_cache(draw_buf, &area_to_draw);

On CLang this will result in the following warning:
passing 'const lv_draw_buf_t *' to parameter of type 'lv_draw_buf_t *' discards qualifiers [-Wincompatible-pointer-types-discards-qualifiers]

And since draw_buf itself should not be affected by cache management operations on draw_buf->data it felt right to propagate the constness requirement.