ima: Fix misuse of dereference of pointer in template_desc_init_fields()

ima: Fix misuse of dereference of pointer in template_desc_init_fields()

[ Upstream commit 47460872ad2c8f019255d1df5451896334d057dd ]

The input parameter @fields is type of struct ima_template_field ***, so
when allocates array memory for @fields, the size of element should be
sizeof(**field) instead of sizeof(*field).

Actually the original code would not cause any runtime error, but it's
better to make it logically right.

Fixes: 2c7192a88a90 ("ima: new templates management mechanism")
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Reviewed-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>