Base: Remove mentioned pci_ecam per-device option from boot_paramters(7)

This option was removed and can't be used anymore.

Base/usr/share/man/man7/boot_parameters.md

@@ -49,7 +49,7 @@ List of options:
 * **`init_args`** - This parameter expects a set of arguments to pass to the **`init`** program.
   The value should be a set of strings separated by `,` characters.
 
-* **`pci_ecam`** - This parameter expects **`on`** or **`off`**, or **`per-device`**.
+* **`pci_ecam`** - This parameter expects **`on`** or **`off`**.
 
 * **`root`** - This parameter configures the device to use as the root file system. It defaults to **`/dev/hda`** if unspecified.