app: aboot: Verify boot image signature
app: aboot: Verify boot image signature

Verify boot image signature as part of fastboot boot
command and fix buffer over read issues by sanitize
the kernel, ramdisk, page size read from boot image
header.

CRs-Fixed: 681957 682002
Change-Id: I546502c7a9479c8a41453e32c6cb14bc850709fe

Redmi-dev/android_bootable_lk,Redmi-dev/android_bootable_lk,Redmi-dev/android_bootable_lk,Redmi-dev/android_bootable_lk,Redmi-dev/android_bootable_lk