rauc.1, src/mbr: fix typos

These typos show up when building the package for Debian, the Lintian
tool can be picky:

~~~~
$ lintian ../rauc_1.2-1_amd64.changes
I: rauc: spelling-error-in-binary usr/bin/rauc multipe multiple
I: rauc: spelling-error-in-manpage usr/share/man/man1/rauc.1.gz allows to allows one to
~~~~

Actually there are many more "allows to" in RAUC codebase, which indeed
seems to be a common mistake according to [1]. Replacing by "allows one"
or "allows us" or something else? I'm not a native English speaker, I
can't say, so I prefer not to touch it, except for the one that Lintian
complains about :)

[1]: https://www.impan.pl/wydawnictwa/dla-autorow/errors.pdf

Signed-off-by: Arnaud Rebillout <arnaud.rebillout@collabora.com>

rauc.1

@@ -174,7 +174,7 @@ The subcommands \fBmark-good\fR and \fBmark-bad\fR can be used to set the state
 explicitly. These subcommands usually operate on the currently booted slot if not specified per
 additional parameter.
 
-The subcommand \fBmark-active\fR allows to manually switch to a different slot. Here too,
+The subcommand \fBmark-active\fR allows one to manually switch to a different slot. Here too,
 the desired slot can be given per parameter, otherwise the currently booted one is used.
 
 \fBOptions:\fR

src/mbr.c

@@ -235,7 +235,7 @@ static gboolean get_raw_partition_entry(gint fd,
 
 	if (partition->start % sector_size || partition->size % sector_size) {
 		g_set_error(error, R_UPDATE_ERROR, R_UPDATE_ERROR_FAILED,
-				"Partition start address or size is not a multipe"
+				"Partition start address or size is not a multiple"
 				" of sector size %d", sector_size);
 		goto out;
 	}