[IA64] acpi_get_sysname() should be __init

Section mismatch: reference to .init.text:acpi_find_rsdp
 (between 'acpi_get_sysname' and 'acpi_request_vector')

acpi_get_sysname() needs to call the __init function acpi_find_rsdp, but it
doesn't have the __init attribute itself, hence the warning. Luckily it is
only called from machvec_init() which has __init attribute, so the fix
is to define acpi_get_sysname() as __init too.

Signed-off-by: Tony Luck <tony.luck@intel.com>