Claude review: drm/sysfb: Fix efidrm error handling and memory type mismatch

[Claude Code Review Bot <claude-review@example.com>]

Overall Series Review

Subject: drm/sysfb: Fix efidrm error handling and memory type mismatch
Author: Chen Ni <nichen@iscas.ac.cn>
Patches: 2
Reviewed: 2026-03-12T07:16:10.625324

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This is a single-patch series fixing two real bugs in `efidrm_device_create()`:

1. **Incorrect error checking for `devm_memremap()`**: The original code checks `if (!screen_base)`, but `devm_memremap()` returns `ERR_PTR()` on failure, not `NULL`. So the error path was never triggered for the WT/WB cases.

2. **`iosys_map` type mismatch**: `devm_memremap()` returns `void *` (system memory), but the original code unconditionally calls `iosys_map_set_vaddr_iomem()` which sets `is_iomem = true`. For WT/WB memory, `iosys_map_set_vaddr()` (which sets `is_iomem = false`) should be used instead.

Both are legitimate bugs. The fix is correct in approach and addresses both issues properly.

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