fbdev: imsttfb: fix a resource leak in probe

stable inclusion
from stable-v6.6.2
commit b346a531159d08c564a312a9eaeea691704f3c00
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8IW7G

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b346a531159d08c564a312a9eaeea691704f3c00



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[ Upstream commit aba6ab57a910ad4b940c2024d15f2cdbf5b7f76b ]

I've re-written the error handling but the bug is that if init_imstt()
fails we need to call iounmap(par->cmap_regs).

Fixes: c75f5a55 ("fbdev: imsttfb: Fix use after free bug in imsttfb_probe")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>