Documentation: firmware-guide/ACPI: correct spelling

Correct spelling problems for Documentation/firmware-guide/ as reported
by codespell.

Signed-off-by: Randy Dunlap <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

Documentation/firmware-guide/acpi/acpi-lid.rst

···
 _LID control method is evaluated during the runtime, the problem is its
 initial returning value. When the AML tables implement this control method
 with cached value, the initial returning value is likely not reliable.
-There are platforms always retun "closed" as initial lid state.
+There are platforms always return "closed" as initial lid state.
 
 Restrictions of the lid state change notifications
 ==================================================

Documentation/firmware-guide/acpi/namespace.rst

···
 Description Table) using its first entry, the data within the FADT
 includes various fixed-length entries that describe fixed ACPI features
 of the hardware.  The FADT contains a pointer to the DSDT
-(Differentiated System Descripition Table).  The XSDT also contains
+(Differentiated System Description Table).  The XSDT also contains
 entries pointing to possibly multiple SSDTs (Secondary System
 Description Table).