bus_dma.9: Fix two typos in the manual page

- s/decribes/describes/
- s/Muliple/Multiple/

MFC after:	5 days

share/man/man9/bus_dma.9

@@ -197,7 +197,7 @@ in addition to restrictions that differ between unrelated groups of
 transactions,
 the driver can first create a
 .Dq parent
-tag that decribes the common restrictions.
+tag that describes the common restrictions.
 The per-group tags can then inherit these restrictions from this
 .Dq parent
 tag rather than having to list them explicitly when creating the per-group tags.
@@ -733,7 +733,7 @@ Fills in the selected fields of the template with a variable number of
 key-value parameters.
 The macros listed below take an argument of the specified type and encapsulate
 it into a key-value structure that is directly usable as a parameter argument.
-Muliple parameters may be provided at once.
+Multiple parameters may be provided at once.
 .Bd -literal
 	BD_PARENT()	void *
 	BD_ALIGNMENT()	uintmax_t