Docs/arch/arm64: Fix spelling in amu.rst

Change though to through.

Signed-off-by: Gabriel <gshahrouzi@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/67bd05b5.c80a0220.205997.19df@mx.google.com

Author: gShahr

Documentation/arch/arm64/amu.rst

@@ -80,7 +80,7 @@ bypass the setting of AMUSERENR_EL0 to trap accesses from EL0 (userspace) to
 EL1 (kernel). Therefore, firmware should still ensure accesses to AMU registers
 are not trapped in EL2/EL3.
 
-The fixed counters of AMUv1 are accessible though the following system
+The fixed counters of AMUv1 are accessible through the following system
 register definitions:
 
  - SYS_AMEVCNTR0_CORE_EL0