Spelling errors in environment variables of meta-security

[George Liu]

Hey Armin Kuster:
  When I wanted to eliminate the alarm message by disabling
SKIP_META_SECURITY_SANITY_CHECK, I found that the environment variable
in [1] was misspelled, Armin Kuster, can you fix this problem? thanks
so much.

openBMC URL: https://github.com/openbmc/openbmc/blob/master/meta-security/classes/sanity-meta-security.bbclass#L4

[1]: git://git.yoctoproject.org/meta-security(c1235f6affb5c38e64b3a04533b8388969b194b2)