docs: Fix typos, improve grammar in Userspace API

Fix a typo and improve wording and punctuation in
the documentation for Userspace API.

Reviewed-by: Mark Pearson <[e-mail]>
Signed-off-by: Hanne-Lotta Mäenpää <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jonathan Corbet <[e-mail]>

Documentation/userspace-api/sysfs-platform_profile.rst

···
 Note that this API is only for selecting the platform profile, it is
 NOT a goal of this API to allow monitoring the resulting performance
 characteristics. Monitoring performance is best done with device/vendor
-specific tools such as e.g. turbostat.
+specific tools, e.g. turbostat.
 
-Specifically when selecting a high performance profile the actual achieved
+Specifically, when selecting a high performance profile the actual achieved
 performance may be limited by various factors such as: the heat generated
 by other components, room temperature, free air flow at the bottom of a
 laptop, etc. It is explicitly NOT a goal of this API to let userspace know
···
 "Custom" profile support
 ========================
 The platform_profile class also supports profiles advertising a "custom"
-profile. This is intended to be set by drivers when the setttings in the
+profile. This is intended to be set by drivers when the settings in the
 driver have been modified in a way that a standard profile doesn't represent
 the current state.