target: Remove WEAK definition of target_read_panel_signature
target: Remove WEAK definition of target_read_panel_signature

Function target_read_panel_signature to be moved to msm shared.
Hence remove WEAK definition from target init.

Change-Id: I37d9268971d6050913c995ef5cec1b1111a5ae5b

lg-devs/g2-bootloader,idor/dk50-bootable_bootloader_lk,t2m-foxfone/android_kernel_lk,mozilla-b2g/fairphone2_kernel_lk,idor/dk50-bootable_bootloader_lk,lg-devs/g2-bootloader,t2m-foxfone/android_kernel_lk,t2m-foxfone/android_kernel_lk,lg-devs/g2-bootloader,mozilla-b2g/fairphone2_kernel_lk,mozilla-b2g/fairphone2_kernel_lk,t2m-foxfone/android_kernel_lk,t2m-foxfone/android_kernel_lk,mozilla-b2g/fairphone2_kernel_lk,idor/dk50-bootable_bootloader_lk,lg-devs/g2-bootloader,idor/dk50-bootable_bootloader_lk,mozilla-b2g/fairphone2_kernel_lk,lg-devs/g2-bootloader,idor/dk50-bootable_bootloader_lk