fix(pm_low_power_modes): Move extra LPM confirmation to AM62X only

The PMIC_LPM_EN signal stays high when the device is in DeepSleep or MCU
Only for AM62P and AM62A. It can only go low in DeepSleep when
programmed on AM62X. Reword and move the extra confirmation to only
appear in AM62X documentation.

Signed-off-by: Kendall Willis <k-willis@ti.com>

Author: kwillis01

source/linux/Foundational_Components/Power_Management/pm_low_power_modes.rst

@@ -274,9 +274,12 @@ In order to enter Deep Sleep, use the following command:
       [  230.295457] psci: CPU3 killed (polled 0 ms)
 
 This partially indicates that Linux has finished it's Deep Sleep suspend sequence.
-For further confirmation, one can take a look at the PMIC_LPM_EN pin on the EVM
-(after programming the PMCTRL_SYS register (0x43018080) to 0x15). Here, if the pin is 3.3V when active and
-0V when in deep sleep.
+
+.. ifconfig:: CONFIG_part_variant in ('AM62X')
+
+   For further confirmation, program the PMCTRL_SYS register (0x43018080) to
+   0x15. The PMIC_LPM_EN pin on the EVM is 3.3V when active and 0V when in 
+   DeepSleep.
 
 .. note::