Claude review: drm/panel: himax-hx83102: restore MODE_LPM after sending disable cmds

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

Patch Review

**Analysis of the bug:**

At probe time (line 1173-1174), `mode_flags` is initialized with `MIPI_DSI_MODE_LPM` set:
```c
dsi->mode_flags = MIPI_DSI_MODE_VIDEO | MIPI_DSI_MODE_VIDEO_SYNC_PULSE |
                  MIPI_DSI_MODE_LPM;
```

In `hx83102_disable()`, `MIPI_DSI_MODE_LPM` is cleared at line 935:
```c
dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
```

Before this patch, the flag was never restored. The `unprepare` function (line 947) doesn't issue any DSI commands — it only toggles GPIOs and regulators — so the missing flag persists into the next `prepare`/`init` cycle. Since the init sequences send many DSI commands expecting LP mode, this breaks the second panel enable.

**The fix** (line 940):
```c
dsi->mode_flags |= MIPI_DSI_MODE_LPM;
```

This is placed after the two DSI DCS commands (`set_display_off` and `enter_sleep_mode`) and before the `mipi_dsi_msleep()`. The placement is correct — the disable commands that need HS mode have already been sent, and restoring LPM before the sleep is harmless (the sleep helper only touches the error accumulator and calls `msleep`, it doesn't send a DSI command that would be affected by the mode flag).

**Consistency with existing code:** The backlight functions in the same file (`hx83102_bl_update_status` at lines 1064-1070 and `hx83102_bl_get_brightness` at lines 1081-1087) use the exact same clear-before/restore-after pattern. This patch makes `hx83102_disable` consistent with those.

**Minor observation:** The commit message and `Fixes:` tag are well-formed. The `Cc: stable@vger.kernel.org # 6.11+` annotation is appropriate since the bug was introduced by the refactoring in commit `0ef94554dc40`.

**No issues found.**

Reviewed-by tag recommendation: This patch is ready to be applied as-is.

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