aspeed: Fix a potential memory leak bug in write_boot_rom()

aspeed: Fix a potential memory leak bug in write_boot_rom()

A memory chunk is allocated with g_new0() and assigned to the variable
'storage'. However, if the branch takes true, there will be only an
error report but not a free operation for 'storage' before function
returns. As a result, a memory leak bug is triggered.

Use g_autofree to fix the issue.

Suggested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Wentao_Liang <Wentao_Liang_g@163.com>
[ clg: reworked the commit log ]
Signed-off-by: Cédric Le Goater <clg@kaod.org>