In case of error, the function devm_ioremap() returns NULL pointer not ERR_PTR().
The IS_ERR() test in the return value check should be replaced with NULL test.
After that, the error code -ENOMEM should be returned.
Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
Signed-off-by: Qiheng Lin <linqiheng@xxxxxxxxxx>