ARM: prima2: pm: drop redundant postcore_initcall

This will delete some redundant calling of sirfsoc_of_pwrc_init() and
sirfsoc_memc_init() for non-CSR platforms if we use multi-platform.

Cc: Srinivas Kandagatla <srinivas.kandagatla@st.com>
Signed-off-by: Barry Song <Baohua.Song@csr.com>
Signed-off-by: Olof Johansson <olof@lixom.net>