fix(configs): AM69/AM69A: Remove PCIe Backplane Documentation

The SK-AM69 EVM has only one PCIe card slot, whereas the PCIe backplane
functionality requires at least two PCIe endpoints. Therefore, PCIe
backplane functionality cannot be used on this platform.

Signed-off-by: Aksh Garg <a-garg7@ti.com>

Author: AkshGarg-19

configs/AM69/AM69_linux_toc.txt

@@ -66,7 +66,6 @@ linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-CBS
 linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-IET
 linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-TSN-Tuning
 linux/Foundational_Components/Kernel/Kernel_Drivers/PCIe/PCIe_End_Point
-linux/Foundational_Components/Kernel/Kernel_Drivers/PCIe/PCIe_Backplane
 linux/Foundational_Components/Kernel/Kernel_Drivers/PCIe/PCIe_Root_Complex
 linux/Foundational_Components/Kernel/Kernel_Drivers/PMIC/pmic_tps6594
 linux/Foundational_Components_Power_Management

configs/AM69A/AM69A_linux_toc.txt

@@ -66,7 +66,6 @@ linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-CBS
 linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-IET
 linux/Foundational_Components/Kernel/Kernel_Drivers/Network/CPSW-TSN-Tuning
 linux/Foundational_Components/Kernel/Kernel_Drivers/PCIe/PCIe_End_Point
-linux/Foundational_Components/Kernel/Kernel_Drivers/PCIe/PCIe_Backplane
 linux/Foundational_Components/Kernel/Kernel_Drivers/PCIe/PCIe_Root_Complex
 linux/Foundational_Components/Kernel/Kernel_Drivers/PMIC/pmic_tps6594
 linux/Foundational_Components_Power_Management