kexec: Make --status work with normal kexec images

According to kexec(8) manpage, --status (-S) works with both
normal kexec (loaded by -l) and crash kernel (loaded by -p) image
types, and defaults to the latter. However, the implementation does
not match the description: `kexec -l -S` queries the -p image type
as if -l were not specified. This is because there is no internal
flag defined for the normal kexec type, and -S treats the zero flag
as the trigger for the default behaviour (-p).

Fix that by making sure the default behaviour for -S is not applied
when the -l option is present.

Signed-off-by: Raphael Ning <raphning@amazon.com>
Signed-off-by: Simon Horman <horms@verge.net.au>