docs/system: remove excessive punctuation from guest-loader docs

A possessive its needs no ' whereas the contraction of it is does.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20230424092249.58552-16-alex.bennee@linaro.org>

docs/system/guest-loader.rst

@@ -14,7 +14,7 @@ The guest loader does two things:
   - load blobs (kernels and initial ram disks) into memory
   - sets platform FDT data so hypervisors can find and boot them
 
-This is what is typically done by a boot-loader like grub using it's
+This is what is typically done by a boot-loader like grub using its
 multi-boot capability. A typical example would look like:
 
 .. parsed-literal::
@@ -25,9 +25,9 @@ multi-boot capability. A typical example would look like:
     -device guest-loader,addr=0x47000000,initrd=rootfs.cpio
 
 In the above example the Xen hypervisor is loaded by the -kernel
-parameter and passed it's boot arguments via -append. The Dom0 guest
+parameter and passed its boot arguments via -append. The Dom0 guest
 is loaded into the areas of memory. Each blob will get
-``/chosen/module@<addr>`` entry in the FDT to indicate it's location and
+``/chosen/module@<addr>`` entry in the FDT to indicate its location and
 size. Additional information can be passed with by using additional
 arguments.